Wide temperature range ultracapacitor

ABSTRACT

A solid state polymer electrolyte is disclosed for use in an ultracapacitor. The electrolyte includes an ionic liquid and a polymer and may include other additives, wherein an ultracapacitor that utilizes the solid state electrolyte is configured to output electrical energy at temperatures between about −40° C. and about 250° C. or more.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.15/660,950, filed Jul. 26, 2017, now U.S. Pat. No. 11,127,537, grantedSep. 21, 2021, which is a continuation of International PatentApplication No. PCT/US2016/015237, filed Jan. 27, 2016, which claims thebenefit of each of U.S. Provisional Application Nos. 62/108,162 and62/108,494, each filed Jan. 27, 2015 and U.S. Provisional ApplicationNos. 62/269,063 and 62/269,077, each filed Dec. 17, 2015. The contentsof this application are also related to International Publication No.WO201510271 published Aug. 9, 2015. The disclosures of the aforesaidapplications are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with support under government grant Contract No.NNX15CC71P awarded by the National Aeronautics and Space Administration(NASA), Contract No. NNX15CP59P awarded by the National Aeronautics andSpace Administration (NASA). The U.S. government may have rights in thisinvention.

BACKGROUND

The invention disclosed herein relates to energy storage cells, and inparticular to techniques for providing an electric double-layercapacitor that is operable at high temperatures.

Energy storage cells are ubiquitous in our society. While most peoplerecognize an energy storage cell simply as a “battery,” other types ofcells may be included. For example, recently, ultracapacitors havegarnered much attention as a result of their favorable characteristics.In short, many types of energy storage cells are known and in use today.

As a general rule, an energy storage cell includes an energy storagemedia disposed within a housing (such as a canister). While a metalliccanister can provide robust physical protection for the cell, such acanister is typically both electrically and thermally conductive and canreact with the energy storage cell. Typically, such reactions increasein rate as ambient temperature increases. The electrochemical or otherproperties of many canisters can cause poor initial performance and leadto premature degradation of the energy storage cell, especially atelevated temperatures.

In fact, a variety of factors work to degrade performance of energystorage systems at elevated temperatures. Thus, what are needed aremethods and apparatus for improving performance of an electricdouble-layer capacitor (EDLC) at elevated temperatures. Preferably, themethods and apparatus result in improved performance at a minimal cost.

One factor that negatively affects EDLC performance at elevatedtemperatures is the degradation of electrolyte at elevated temperatures.A variety of electrolytes are used in EDLCs, but only a few are stableenough at elevated temperatures to be used in high temperature energystorage cells. Moreover, the available electrolytes typically do notperform adequately at temperatures over about 200° C. Certainapplications require energy storage cells that are capable of operatingat temperatures in excess of about 200° C., e.g., subsurface drilling,such as petroleum exploration and geothermal wells. Moreover, in certaindemanding applications, the available electrolytes do not performadequately at temperatures over about 150° C. Therefore, electrolytesare needed to extend the operating temperature range of high temperatureenergy storage cells, particularly EDLCs, to temperatures over about200° C. Also desirable are electrolytes that are capable of performingover a wide range temperatures, e.g., down to very low temperatures suchas −40° C. or even −110° C. and below.

Although typically necessary in any EDLC to prevent contact between theelectrodes, the separator frequently introduces undesirablecharacteristics to EDLCs, e.g., contamination and decomposition.However, available EDLCs cannot work without a separator to preventcontact between the electrodes, i.e., a short circuit. Therefore, aseparator-less EDLC would be desirable to improve the properties of theEDLC.

The foregoing Background section is provided for informational purposesonly, and does not constitute an admission that any of the informationcontained therein is prior art to the present application.

SUMMARY

In one aspect, a solid state polymer electrolyte is disclosed for use inan ultracapacitor. The electrolyte includes an ionic liquid and apolymer and may include other additives, wherein an ultracapacitor thatutilizes the solid state electrolyte is configured to output electricalenergy at temperatures between about −40° C. and about 250° C., 275° C.,300° C., 350° C., or more.

In certain embodiments, other additives are mixed with the polymer,e.g., gelling agents (e.g., silica or silicates), other inorganic orceramic powders (e.g., alumina, titania, magnesia, aluminosilicates, ortitanates such as BaTiO₃), clays (e.g., bentonite or montmorillonite andtheir derivatives), solvents, other polymeric materials, plasticizers,and combinations thereof.

In another aspect, an apparatus is disclosed comprising an electricdouble layer capacitor having a on operational temperature rangecomprising −110 C to 80 C, or any subrange thereof.

In some embodiments, the capacitor comprises an electrolyte comprising:a salt; a first solvent; and a second solvent; wherein a melting pointof the first solvent is greater than a melting point of the secondsolvent; wherein a dielectric constant of the first solvent is greaterthan a dielectric constant of the second solvent.

In some embodiments, the capacitor comprises a pressurized housingcontaining an electrolyte comprising: a salt; a first solvent, whereinthe first solvent is a gas at a temperature of 0 C and a pressure of 760mmHg.

Various embodiments may include any of the features described above orin the listing of claims provided herein, alone, or in any suitablecombination.

BRIEF DESCRIPTION OF THE DRAWINGS

The skilled artisan will understand that the drawings primarily are forillustrative purposes and are not intended to limit the scope of theinventive subject matter described herein. The drawings are notnecessarily to scale; in some instances, various aspects of theinventive subject matter disclosed herein may be shown exaggerated orenlarged in the drawings to facilitate an understanding of differentfeatures. In the drawings, like reference characters generally refer tolike features (e.g., functionally similar and/or structurally similarelements).

FIG. 1A illustrates aspects of an exemplary ultracapacitor that employsa separator.

FIG. 1B illustrates aspects of an exemplary ultracapacitor without aseparator.

FIG. 2 is a block diagram depicting a plurality of carbon nanotubes(CNT) grown onto a substrate.

FIG. 3 is a block diagram depicting deposition of a current collectoronto the CNT of FIG. 2 to provide an electrode element.

FIG. 4 is a block diagram depicting addition of transfer tape to theelectrode element of FIG. 3.

FIG. 5 is a block diagram depicting the electrode element during atransfer process.

FIG. 6 is a block diagram depicting the electrode element subsequent totransfer.

FIG. 7 is a block diagram depicting an exemplary electrode fabricatedfrom a plurality of the electrode elements.

FIG. 8 depicts embodiments of primary structures for cations that may beincluded in the exemplary ultracapacitor.

FIG. 9 illustrates aspects of an exemplary ultracapacitor that employs asolid state electrolyte.

FIG. 10 illustrates am electron micrograph of an ionic liquid dopedpolymer matrix.

FIG. 11 illustrates am electron micrograph of purified carbon nanotubes.

FIG. 12 shows a table of exemplary solvents.

FIG. 13 shows a table of exemplary anions and cations.

FIG. 14A is part one of a table showing exemplary ultracapacitorperformance.

FIG. 14B is part two of a table showing exemplary ultracapacitorperformance, rows continue from FIG. 14A.

FIG. 15 illustrates a pyro initiator for use in stage separation of alaunch vehicle.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, inventive methods and apparatus forenergy storage devices. It should be appreciated that various conceptsintroduced above and discussed in greater detail below may beimplemented in any of numerous ways, as the disclosed concepts are notlimited to any particular manner of implementation. Examples of specificimplementations and applications are provided primarily for illustrativepurposes.

In general, the capacitor includes energy storage media that is adaptedfor providing high power density and high energy density when comparedto prior art devices. The capacitor includes components that areconfigured for ensuring operation over the temperature range, andincludes any one or more of a variety of forms of electrolyte that arelikewise rated for the temperature range. The combination ofconstruction, energy storage media and electrolyte result incapabilities to provide robust operation under extreme conditions. Toprovide some perspective, aspects of an exemplary embodiment are nowintroduced.

Referring to FIGS. 1A and 1B, exemplary embodiments of a capacitor areshown. In each case, the capacitor is an “ultracapacitor 10.” Thedifference between FIG. 1A and FIG. 1B is the inclusion of a separatorin exemplary ultracapacitor 10 of FIG. 1A. The concepts disclosed hereingenerally apply equally to any exemplary ultracapacitor 10. Certainelectrolytes of certain embodiments are uniquely suited to constructingan exemplary ultracapacitor 10 without a separator. Unless otherwisenoted, the discussion herein applies equally to any ultracapacitor 10,with or without a separator.

The exemplary ultracapacitor 10 is an electric double-layer capacitor(EDLC). The EDLC includes at least one pair of electrodes 3 (where theelectrodes 3 may be referred to as a negative electrode 3 and a positiveelectrode 3, merely for purposes of referencing herein). When assembledinto the ultracapacitor 10, each of the electrodes 3 presents a doublelayer of charge at an electrolyte interface. In some embodiments, aplurality of electrodes 3 is included (for example, in some embodiments,at least two pairs of electrodes 3 are included). However, for purposesof discussion, only one pair of electrodes 3 are shown. As a matter ofconvention herein, at least one of the electrodes 3 uses a carbon-basedenergy storage media 1 (as discussed further herein) to provide energystorage. However, for purposes of discussion herein, it is generallyassumed that each of the electrodes includes the carbon-based energystorage media 1. It should be noted that a conventional electrolyticcapacitor differs from an ultracapacitor because conventional metallicelectrodes differ greatly (at least an order of magnitude) in surfacearea.

Each of the electrodes 3 includes a respective current collector 2 (alsoreferred to as a “charge collector”). In some embodiments, theelectrodes 3 are separated by a separator 5. In general, the separator 5is a thin structural material (usually a sheet) used to separate thenegative electrode 3 from the positive electrode 3. The separator 5 mayalso serve to separate pairs of the electrodes 3. Once assembled, theelectrodes 3 and the separator 5 provide a storage cell 12. Note that,in some embodiments, the carbon-based energy storage media 1 may not beincluded on one or both of the electrodes 3. That is, in someembodiments, a respective electrode 3 might consist of only the currentcollector 2. The material used to provide the current collector 2 couldbe roughened, anodized or the like to increase a surface area thereof.In these embodiments, the current collector 2 alone may serve as theelectrode 3. With this in mind, however, as used herein, the term“electrode 3” generally refers to a combination of the energy storagemedia 1 and the current collector 2 (but this is not limiting, for atleast the foregoing reason).

At least one form of electrolyte 6 is included in the ultracapacitor 10.The electrolyte 6 fills void spaces in and between the electrodes 3 andthe separator 5. In general, the electrolyte 6 is a substance thatdisassociates into electrically charged ions. A solvent that dissolvesthe substance may be included in some embodiments of the electrolyte 6,as appropriate. The electrolyte 6 conducts electricity by ionictransport.

Generally, the storage cell 12 is formed into one of a wound form orprismatic form which is then packaged into a cylindrical or prismatichousing 7. Once the electrolyte 6 has been included, the housing 7 maybe hermetically sealed. In various examples, the package is hermeticallysealed by techniques making use of laser, ultrasonic, and/or weldingtechnologies. In addition to providing robust physical protection of thestorage cell 12, the housing 7 is configured with external contacts toprovide electrical communication with respective terminals 8 within thehousing 7. Each of the terminals 8, in turn, provides electrical accessto energy stored in the energy storage media 1, generally throughelectrical leads which are coupled to the energy storage media 1.

As discussed herein, “hermetic” refers to a seal whose quality (i.e.,leak rate) is defined in units of “atm-cc/second,” which means one cubiccentimeter of gas (e.g., He) per second at ambient atmospheric pressureand temperature. This is equivalent to an expression in units of“standard He-cc/sec.” Further, it is recognized that 1 atm-cc/sec isequal to 1.01325 mbar-liter/sec. Generally, the ultracapacitor 10disclosed herein is capable of providing a hermetic seal that has a leakrate no greater than about 5.0×10⁻⁶ atm-cc/sec, and may exhibit a leakrate no higher than about 5.0×10⁻¹⁰ atm-cc/sec. It is also consideredthat performance of a successfully hermetic seal is to be judged by theuser, designer or manufacturer as appropriate, and that “hermetic”ultimately implies a standard that is to be defined by a user, designer,manufacturer or other interested party.

Leak detection may be accomplished, for example, by use of a tracer gas.Using tracer gas such as helium for leak testing is advantageous as itis a dry, fast, accurate and non destructive method. In one example ofthis technique, the ultracapacitor 10 is placed into an environment ofhelium. The ultracapacitor 10 is subjected to pressurized helium. Theultracapacitor 10 is then placed into a vacuum chamber that is connectedto a detector capable of monitoring helium presence (such as an atomicabsorption unit). With knowledge of pressurization time, pressure andinternal volume, the leak rate of the ultracapacitor 10 may bedetermined.

In some embodiments, at least one lead (which may also be referred toherein as a “tab”) is electrically coupled to a respective one of thecurrent collectors 2. A plurality of the leads (accordingly to apolarity of the ultracapacitor 10) may be grouped together and coupledto into a respective terminal 8. In turn, the terminal 8 may be coupledto an electrical access, referred to as a “contact” (e.g., one of thehousing 7 and an external electrode (also referred to herein forconvention as a “feed-through” or “pin”)).

Consider now the energy storage media 1 in greater detail. In theexemplary ultracapacitor 10, the energy storage media 1 is formed ofcarbon nanotubes. The energy storage media 1 may include othercarbonaceous materials including, for example, activated carbon, carbonfibers, rayon, graphene, aerogel, carbon cloth, and a plurality of formsof carbon nanotubes. Activated carbon electrodes can be manufactured,for example, by producing a carbon base material by carrying out a firstactivation treatment to a carbon material obtained by carbonization of acarbon compound, producing a formed body by adding a binder to thecarbon base material, carbonizing the formed body, and finally producingan active carbon electrode by carrying out a second activation treatmentto the carbonized formed body. Carbon fiber electrodes can be produced,for example, by using paper or cloth pre-form with high surface areacarbon fibers.

In some embodiments, the electrode of the ultracapacitor 10 includes acurrent collector comprising aluminum with an aluminum carbide layer onat least one surface, on which at least one layer of carbon nanotubes(CNTs) is disposed. The electrode may comprise vertically-aligned,horizontally-aligned, or nonaligned (e.g., tangled or clustered) CNTs.The electrode may comprise compressed CNTs. The electrode may comprisesingle-walled, double-walled, or multiwalled CNTs. The electrode maycomprise multiple layers of CNTs. In some embodiments, the carbide layerincludes elongated whisker structures with a nanoscale width. In someembodiments, the whiskers protrude into the layer of CNTs. In someembodiments, the whiskers protrude through an intervening layer (e.g.,an oxide layer) into the layer of CNTs. Further details relating toelectrodes of this type may be found in U.S. Provisional PatentApplication No. 62/061,947 “ELECTRODE FOR ENERGY STORAGE DEVICE USINGANODIZED ALUMINUM” filed Oct. 9, 2014, International Application No.PCT/US15/55032 “NANOSTRUCTURED ELECTRODE FOR ENERGY STORAGE DEVICE”,filed Oct. 9, 2015, the entire contents of which are incorporated hereinby reference.

In an exemplary method for fabricating carbon nanotubes, an apparatusfor producing an aligned carbon-nanotube aggregate includes apparatusfor synthesizing the aligned carbon-nanotube aggregate on a basematerial having a catalyst on a surface thereof. The apparatus includesa formation unit that processes a formation step of causing anenvironment surrounding the catalyst to be an environment of a reducinggas and heating at least either the catalyst or the reducing gas; agrowth unit that processes a growth step of synthesizing the alignedcarbon-nanotube aggregate by causing the environment surrounding thecatalyst to be an environment of a raw material gas and by heating atleast either the catalyst or the raw material gas; and a transfer unitthat transfers the base material at least from the formation unit to thegrowth unit. A variety of other methods and apparatus may be employed toprovide the aligned carbon-nanotube aggregate.

In some embodiments, material used to form the energy storage media 1may include material other than pure carbon (and the various forms ofcarbon as may presently exist or be later devised). That is, variousformulations of other materials may be included in the energy storagemedia 1. More specifically, and as a non-limiting example, at least onebinder material may be used in the energy storage media 1, however, thisis not to suggest or require addition of other materials (such as thebinder material). In general, however, the energy storage media 1 issubstantially formed of carbon, and may therefore referred to herein asa “carbonaceous material,” as a “carbonaceous layer” and by othersimilar terms. In short, although formed predominantly of carbon, theenergy storage media 1 may include any form of carbon (as well as anyadditives or impurities as deemed appropriate or acceptable) to providefor desired functionality as energy storage media 1.

In one set of embodiments, the carbonaceous material includes at leastabout 60% elemental carbon by mass, and in other embodiments at leastabout 75%, 85%, 90%, 95% or 98%) by mass elemental carbon.

Carbonaceous material can include carbon in a variety forms, includingcarbon black, graphite, and others. The carbonaceous material caninclude carbon particles, including nanoparticles, such as nanotubes,nanorods, graphene sheets in sheet form, and/or formed into cones, rods,spheres (buckyballs) and the like.

Some embodiments of various forms of carbonaceous material suited foruse in energy storage media 1 are provided herein as examples. Theseembodiments provide robust energy storage and are well suited for use inthe electrode 3. It should be noted that these examples are illustrativeand are not limiting of embodiments of carbonaceous material suited foruse in energy storage media 1.

In general, the term “electrode” refers to an electrical conductor thatis used to make contact to another material which is often non-metallic,in a device that may be incorporated into an electrical circuit.Generally, the term “electrode,” as used herein, is with reference tothe current collector 2 and the additional components as may accompanythe current collector 2 (such as the energy storage media 1) to providefor desired functionality (for example, the energy storage media 1 whichis mated to the current collector 2 to provide for energy storage andenergy transmission). An exemplary process for complimenting the energystorage media 1 with the current collector 2 to provide the electrode 3is now provided.

Referring now to FIG. 2, a substrate 14 that is host to carbonaceousmaterial in the form of carbon nanotube aggregate (CNT) is shown. In theembodiment shown, the substrate 14 includes a base material 17 with athin layer of a catalyst 18 disposed thereon. [00108] In general, thesubstrate 14 is at least somewhat flexible (i.e., the substrate 14 isnot brittle), and is fabricated from components that can withstandenvironments for deposition of the energy storage media 1 (e.g., CNT).For example, the substrate 14 may withstand a high-temperatureenvironment of between about 400 degrees Celsius to about 1,100 degreesCelsius. A variety of materials may be used for the substrate 14, asdetermined appropriate.

Refer now to FIG. 3. Once the energy storage media 1 (e.g., CNT) hasbeen fabricated on the substrate 14, the current collector 2 may bedisposed thereon. In some embodiments, the current collector 2 isbetween about 0.5 micrometers (μιη) to about 25 micrometers (μιη) thick.In some embodiments, the current collector 2 is between about 20micrometers (μιη) to about 40 micrometers (μιη) thick. The currentcollector 2 may appear as a thin layer, such as layer that is applied bychemical vapor deposition (CVD), sputtering, e-beam, thermal evaporationor through another suitable technique. Generally, the current collector2 is selected for its properties such as conductivity, beingelectrochemically inert and compatible with the energy storage media 1(e.g., CNT). Some exemplary materials include aluminum, platinum, gold,tantalum, titanium, and may include other materials as well as variousalloys.

Once the current collector 2 is disposed onto the energy storage media 1(e.g., CNT), an electrode element 15 is realized. Each electrode element15 may be used individually as the electrode 3, or may be coupled to atleast another electrode element 15 to provide for the electrode 3.

Once the current collector 2 has been fabricated according to a desiredstandard, post-fabrication treatment may be undertaken. Exemplarypost-treatment includes heating and cooling of the energy storage media1 (e.g., CNT) in a slightly oxidizing environment. Subsequent tofabrication (and optional post-treatment), a transfer tool may beapplied to the current collector 2. Reference may be had to FIG. 4.

FIG. 4 illustrates application of transfer tool 13 to the currentcollector 2. In this example, the transfer tool 13 is a thermal releasetape, used in a “dry” transfer method. Exemplary thermal release tape ismanufactured by NITTO DENKO CORPORATION of Fremont, Calif. and Osaka,Japan. One suitable transfer tape is marketed as REV ALPHA. This releasetape may be characterized as an adhesive tape that adheres tightly atroom temperature and can be peeled off by heating. This tape, and othersuitable embodiments of thermal release tape, will release at apredetermined temperature. Advantageously, the release tape does notleave a chemically active residue on the electrode element 15.

In another process, referred to as a “wet” transfer method, tapedesigned for chemical release may be used. Once applied, the tape isthen removed by immersion in a solvent. The solvent is designed todissolve the adhesive.

In other embodiments, the transfer tool 13 uses a “pneumatic” method,such as by application of suction to the current collector 2. Thesuction may be applied, for example, through a slightly oversized paddlehaving a plurality of perforations for distributing the suction. Inanother example, the suction is applied through a roller having aplurality of perforations for distributing the suction. Suction drivenembodiments offer advantages of being electrically controlled andeconomic as consumable materials are not used as a part of the transferprocess. Other embodiments of the transfer tool 13 may be used.

Once the transfer tool 13 has been temporarily coupled to the currentcollector 2, the electrode element 15 is gently removed from thesubstrate 14 (see FIGS. 4 and 5). The removal generally involves peelingthe energy storage media 1 (e.g., CNT) from the substrate 14, beginningat one edge of the substrate 14 and energy storage media 1 (e.g., CNT).

Subsequently, the transfer tool 13 may be separated from the electrodeelement 15 (see FIG. 6). In some embodiments, the transfer tool 13 isused to install the electrode element 15. For example, the transfer tool13 may be used to place the electrode element 15 onto the separator 5.In general, once removed from the substrate 14, the electrode element 15is available for use.

In instances where a large electrode 3 is desired, a plurality of theelectrode elements 15 may be mated. Reference may be had to FIG. 7. Asshown in FIG. 7, a plurality of the electrode elements 15 may be matedby, for example, coupling a coupling 22 to each electrode element 15 ofthe plurality of electrode elements 15. The mated electrode elements 15provide for an embodiment of the electrode 3.

In some embodiments, the coupling 22 is coupled to each of the electrodeelements 15 at a weld 21. Each of the welds 21 may be provided as anultrasonic weld 21. It has been found that ultrasonic welding techniquesare particularly well suited to providing each weld 21. That is, ingeneral, the aggregate of energy storage media 1 (e.g., CNT) is notcompatible with welding, where only a nominal current collector, such asdisclosed herein is employed. As a result, many techniques for joiningelectrode elements 15 are disruptive, and damage the element 15.However, in other embodiments, other forms of coupling are used, and thecoupling 22 is not a weld 21.

The coupling 22 may be a foil, a mesh, a plurality of wires or in otherforms. Generally, the coupling 22 is selected for properties such asconductivity and being electrochemically inert. In some embodiments, thecoupling 22 is fabricated from the same material(s) as are present inthe current collector 2.

In some embodiments, the coupling 22 is prepared by removing an oxidelayer thereon. The oxide may be removed by, for example, etching thecoupling 22 before providing the weld 21. The etching may beaccomplished, for example, with potassium hydroxide (KOH). The electrode3 may be used in a variety of embodiments of the ultracapacitor 10. Forexample, the electrode 3 may be rolled up into a “jelly roll” type ofenergy storage.

The separator 5 may be fabricated from various materials. In someembodiments, the separator 5 is non-woven glass. The separator 5 mayalso be fabricated from fiberglass, ceramics and flouro-polymers, suchas polytetrafiuoroethylene (PTFE), commonly marketed as TEFLON™ byDuPont Chemicals of Wilmington, Del. For example, using non-woven glass,the separator 5 can include main fibers and binder fibers each having afiber diameter smaller than that of each of the main fibers and allowingthe main fibers to be bonded together.

For longevity of the ultracapacitor 10 and to assure performance at hightemperature, the separator 5 should have a reduced amount of impuritiesand in particular, a very limited amount of moisture contained therein.In particular, it has been found that a limitation of about 200 ppm ofmoisture is desired to reduce chemical reactions and improve thelifetime of the ultracapacitor 10, and to provide for good performancein high temperature applications. Some embodiments of materials for usein the separator 5 include polyamide, polytetrafiuoroethylene (PTFE),polyether-ether-ketone (PEEK), aluminum oxide (AI₂O₃), fiberglass,glass-reinforced plastic (GRP), polyester, nylon, and polyphenylenesulfide (PPS).

In general, materials used for the separator 5 are chosen according tomoisture content, porosity, melting point, impurity content, resultingelectrical performance, thickness, cost, availability and the like. Insome embodiments, the separator 5 is formed of hydrophobic materials.

Accordingly, procedures may be employed to ensure excess moisture iseliminated from each separator 5. Among other techniques, a vacuumdrying procedure may be used. A selection of materials for use in theseparator 5 is provided in Table 1. Some related performance data isprovided in Table 2.

TABLE 1 Melting PPM H₂O PPM H₂O Vacuum dry Material point unbaked bakedprocedure Polyamide 256° C. 2052 20 180° C. for 24 hPolytetrafluoroethylene, 327° C. 286 135 150° C. PTFE for 24 h Polyetherether ketone, 256° C. 130 50 215° C. PEEK for 24 h Aluminum Oxide, 330°C. 1600 100 215° C. AI₂O₃ for 24 h Fiberglass (GRP) 320° C. 2000 167215° C. for 24 h

TABLE 2 Separator Performance Data ESR 1^(st) ESR 2^(nd) Material μmPorosity test (Ω) test (Ω) After 10 CV Polyamide 42 Nonwoven 1.069 1.0691.213 PEEK 45 Mesh 1.665 1.675 2.160 PEEK 60% 25 60% 0.829 0.840 0.883Fiberglass 160 Nonwoven 0.828 0.828 0.824 (GRP) Aluminum 25 — 2.4002.400 2.400 Oxide, AI₂O₃

In order to collect data for Table 2, two electrodes 3, based oncarbonaceous material, were provided. The electrodes 3 were disposedopposite to and facing each other. Each of the separators 5 were placedbetween the electrodes 3 to prevent a short circuit. The threecomponents were then wetted with electrolyte 6 and compressed together.Two aluminum bars and PTFE material was used as an external structure toenclose the resulting ultracapacitor 10.

The ESR 1^(st) test and ESR 2^(nd) test were performed with the sameconfiguration one after the other. The second test was run five minutesafter the first test, leaving time for the electrolyte 6 to further soakinto the components.

Note that, in some embodiments, the ultracapacitor 10 does not requireor include the separator 5. For example, in some embodiments, such aswhere the electrodes 3 are assured of physical separation by a geometryof construction, it suffices to have electrolyte 6 alone between theelectrodes 3. More specifically, and as an example of physicalseparation, one such ultracapacitor 10 may include electrodes 3 that aredisposed within a housing such that separation is assured on acontinuous basis. A bench-top example would include an ultracapacitor 10provided in a beaker. A further example may include an ultracapacitorfeaturing a solid state electrolyte, as described in greater detailbelow.

The ultracapacitor 10 may be embodied in several different form factors(i.e., exhibit a certain appearance). Examples of potentially usefulform factors include, a cylindrical cell, an annular or ring-shapedcell, a flat prismatic cell or a stack of flat prismatic cellscomprising a box-like cell, and a flat prismatic cell that is shaped toaccommodate a particular geometry such as a curved space. A cylindricalform factor may be most useful in conjunction with a cylindrical tool ora tool mounted in a cylindrical form factor. An annular or ring-shapedform factor may be most useful in conjunction with a tool that isring-shaped or mounted in a ring-shaped form factor. A flat prismaticcell shaped to accommodate a particular geometry may be useful to makeefficient use of “dead space” (i.e., space in a tool or equipment thatis otherwise unoccupied, and may be generally inaccessible).

While generally disclosed herein in terms of a “jelly roll” application(i.e., a storage cell 12 that is configured for a cylindrically shapedhousing 7), the rolled storage cell may take any form desired. Forexample, as opposed to rolling the storage cell 12, folding of thestorage cell 12 may be performed to provide for the rolled storage cell.Other types of assembly may be used. As one example, the storage cell 12may be a flat cell, referred to as a “coin type” of cell. Accordingly,rolling is merely one option for assembly of the rolled storage cell.Therefore, although discussed herein in terms of being a “rolled storagecell”, this is not limiting. It may be considered that the term “rolledstorage cell” generally includes any appropriate form of packaging orpacking the storage cell 12 to fit well within a given design of thehousing 7.

Various forms of the ultracapacitor 10 may be joined together. Thevarious forms may be joined using known techniques, such as weldingcontacts together, by use of at least one mechanical connector, byplacing contacts in electrical contact with each other and the like. Aplurality of the ultracapacitors 10 may be electrically connected in atleast one of a parallel and a series fashion.

Electrolyte Materials

The electrolyte 6 includes a pairing of cations 9 and anions 11 and mayinclude a solvent or other additives. The electrolyte 6 include an“ionic liquid” as appropriate. Various combinations of cations 9, anions11 and solvent may be used. In the exemplary ultracapacitor 10, thecations 9 may include at least one of tetrabutylammondium,1-(3-Cyanopropyl)-3-methylimidazolium, 1,2-Dimethyl-3-propylimidazolium,1,3-Bis(3-cyanopropyl)imidazolium, 1,3-Diethoxyimidazolium,1-Butyl-1-methylpiperidinium, 1-Butyl-2,3-dimethylimidazolium,1-Butyl-3-methylimidazolium, 1-Butyl-4-methylpyridinium,1-Butylpyridinium, 1-Decyl-3-methylimidazolium,1-Ethyl-3-methylimidazolium, 1-Pentyl-3-methylimidazolium,1-Hexyl-3-methylimidazolium, 3-Methyl-1-propylpyridinium, andcombinations thereof as well as other equivalents as deemed appropriate.Additional exemplary cations 9 include ammonium, imidazolium,pyrazinium, piperidinium, pyridinium, pyrimidinium, and pyrrolidinium(structures of which are depicted in FIG. 8). In the exemplaryultracapacitor 10, the anions 11 may include at least one ofbis(trifluoromethanesulfonate)imide,tris(trifluoromethanesulfonate)methide, dicyanamide, tetrafluoroborate,tetra(cyano)borate, hexafluorophosphate,tris(pentafluoroethyl)trifluorophosphate, trifluoromethanesulfonate,bis(pentafluoroethanesulfonate)imide, thiocyanate,trifluoro(trifluoromethyl)borate, and combinations thereof as well asother equivalents as deemed appropriate.

The solvent may include acetonitrile, amides, benzonitrile,butyrolactone, cyclic ether, dibutyl carbonate, diethyl carbonate,diethylether, dimethoxyethane, dimethyl carbonate, dimethylformamide,dimethyl sulfone, dioxane, dioxolane, ethyl formate, ethylene carbonate,ethylmethyl carbonate, lactone, linear ether, methyl formate, methylpropionate, methyltetrahydrofuran, nitrobenzene, nitromethane,n-methylpyrrolidone, propylene carbonate, sulfolane, sulfone,tetrahydrofuran, tetramethylene sulfone, thiophene, ethylene glycol,diethylene glycol, triethylene glycol, polyethylene glycols, carbonicacid ester, γ-butyrolactone, nitrile, tricyanohexane, any combinationthereof or other material(s) that exhibit appropriate performancecharacteristics.

In certain embodiments, electrolyte 6 may include one or more additionaladditives, e.g., gelling agents (e.g., silica or silicates), otherinorganic or ceramic powders (e.g., alumina, titania, magnesia,aluminosilicates, or titanates such as BaTiO₃), clays (e.g., bentoniteor montmorillonite and their derivatives), solvents, polymeric materials(including polymeric microbeads), plasticizers, and combinationsthereof. Porous inorganic oxides are useful additives for providing agel electrolyte. Exemplary additives include silica, silicates, alumina,titania, magnesia, aluminosilicates, zeolites, or titanates. Forexample, an electrolyte according to one embodiment of the presentinvention comprises an ionic liquid, e.g., one of the ionic liquidsdescribed herein, such as an ionic liquid comprising a cation, asdescribed herein, and an anion, as described herein, and fumed silica asa gelling agent, which are mixed in a ratio to produce an ionic liquidgel. Certain embodiments may employ a different form of silica as agelling agent, e.g., silica gel, mesoporous silica, or amicrocrystalline or polycrystalline form of silica. The amount of theadditive will vary according to the nature of the application and istypically in the range of about 2 wt. % to about 20 wt. %, e.g., about 5wt. % to about 10 wt. %, in the range of potentially as much as about 50wt. %, of the electrolyte.

As discussed herein, water and other contaminants may impedeultracapacitor performance. In certain embodiments, the additivesdescribed herein are dried or otherwise purified prior to incorporatingthem in an ultracapacitor or ultracapacitor electrolyte. For example,the moisture content of the electrolyte comprising an additive, e.g., agelling agent, should be comparable to the ranges described above, e.g.,less than about 1000 ppm, preferably less than about 500 ppm.

A suitable concentration of additive will be determined based on thedesired properties of the electrolyte and/or ultracapacitor, e.g., theviscosity of the electrolyte or the leakage current, capacitance, or ESRof the ultracapacitor. The specific surface area (SSA) also affects theproperties of the electrolyte and the resultant ultracapacitor.Generally, a high SSA is desirable, e.g., above about 100 m²/g, aboveabout 200 m²/g, about 400 m²/g, about 800 m²/g, or about 1000 m²/g. Theviscosity of the electrolyte comprising the additive affects theperformance of the resultant ultracapacitor and must be controlled byadding an appropriate amount of the additive.

In certain embodiments, where an appropriate gel-based electrolyte isemployed, a separator-less ultracapacitor 10 can be prepared, as shownin FIG. 1B. A separator-less ultracapacitor 10 of FIG. 1B is prepared ina manner analogous a typical ultracapacitor having a separator, e.g., anultracapacitor of FIG. 1A, except that the gel-based electrolyte is of asufficient stability that a separator is not required.

In certain embodiments, a solid state polymeric electrolyte may beprepared and employed in an ultracapacitor. In such embodiments, apolymer containing an ionic liquid is cast by dissolving a polymer in asolvent together with an electrolyte and any other additives, e.g.,e.g., gelling agents (e.g., silica or silicates), other inorganic orceramic powders (e.g., alumina, titania, magnesia, aluminosilicates, ortitanates such as BaTiO₃), clays (e.g., bentonite or montmorillonite andtheir derivatives), solvents, other polymeric materials, plasticizers,and combinations thereof. After drying the cast polymer electrolyte filmcan be incorporated into an ultracapacitor using the techniques forassembling ultracapacitors described herein, except that the polymerelectrolyte replaces both the liquid (or gel) electrolyte and theseparator in the ultracapacitor. The polymer film may also be castdirectly onto the electrode of an ultracapacitor. Exemplary polymersinclude polyamide, polytetrafluoroethylene (PTFE), polyvinylidenefluoride-hexafluoropropylene copolymer (PVDF-HFP), polyether etherketone (PEEK), CRAFT, sulfonated poly(ether ether ketone) (SPEEK),crosslinked sulfonated poly(ether ether ketone) (XSPEEK), and otherpolymer and copolymers stable at high temperature and appropriate forhermetic applications.

The advanced electrolyte systems of the present disclosure comprise, inone embodiment, include certain enhanced electrolyte combinationssuitable for use in a temperature range of about minus 40 degreesCelsius to about 250 degrees Celsius, e.g., about minus 10 degreesCelsius to about 250 degrees Celsius, e.g., about minus 5 degreesCelsius to about 250 degrees Celsius e.g., about 0 degrees Celsius toabout 250 degrees Celsius e.g., about minus 20 degrees Celsius to about200 degrees Celsius e.g., about 150 degrees Celsius to about 250 degreesCelsius e.g., about 150 degrees Celsius to about 220 degrees Celsiuse.g., about 150 degrees Celsius to about 200 degrees Celsius, e.g.,about minus 10 degrees Celsius to about 210 degrees Celsius e.g., aboutminus 10 degrees Celsius to about 220 degrees Celsius e.g., about minus10 degrees Celsius to about 230 degrees Celsius. In some embodiments,e.g., where a solid state polymer electrolyte is used, the uppertemperature limit may be increased to more the 250 degrees Celsius,e.g., greater than 300 degrees Celsius or even 350 degrees Celsius.

Generally, a higher degree of durability at a given temperature may becoincident with a higher degree of voltage stability at a lowertemperature. Accordingly, the development of a high temperaturedurability advanced electrolyte system (AES), with enhanced electrolytecombinations, generally leads to simultaneous development of highvoltage, but lower temperature AES, such that these enhanced electrolytecombinations described herein may also be useful at higher voltages, andthus higher energy densities, but at lower temperatures.

In one embodiment, the present invention provides an enhancedelectrolyte combination suitable for use in an energy storage cell,e.g., an ultracapacitor, comprising a novel mixture of electrolytesselected from the group consisting of an ionic liquid mixed with asecond ionic liquid, an ionic liquid mixed with an organic solvent, andan ionic liquid mixed with a second ionic liquid and an organic solventwherein each ionic liquid is selected from the salt of any combinationof the following cations and anions, wherein the cations are selectedfrom the group consisting of 1-butyl-3-methylimidazolium,1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium,1-butyl-1-methylpiperidinium, butyltrimethyl ammonium,1-butyl-1-methylpyrrolidinium, trihexyltetradecylphosphonium, and1-butyl-3-methylimidaxolium; and the anions are selected from the groupconsisting of tetrafluoroborate, bis(trifluoromethylsulfonyl)imide,tetracyanoborate, and trifluoromethanesulfonate; and wherein the organicsolvent is selected from the group consisting of linear sulfones (e.g.,ethyl isopropyl sulfone, ethyl isobutyl sulfone, ethyl methyl sulfone,methyl isopropyl sulfone, isopropyl isobutyl sulfone, isopropyl s-butylsulfone, butyl isobutyl sulfone, and dimethyl sulfone), linearcarbonates (e.g., ethylene carbonate, propylene carbonate, and dimethylcarbonate), and acetonitrile.

For example, given the combinations of cations and anions above, eachionic liquid may be selected from the group consisting of1-butyl-3-methylimidazolium tetrafluoroborate;1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide;1-ethyl-3-methylimidazolium tetrafluoroborate;1-ethyl-3-methylimidazolium tetracyanoborate;1-hexyl-3-methylimidazolium tetracyanoborate;1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide;1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate;1-butyl-1-methylpyrrolidinium tetracyanoborate;trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide,1-butyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide,butyltrimethylammonium bis(trifluoromethylsulfonyl)imide, and1-butyl-3-methylimidazolium trifluoromethanesulfonate.

In certain embodiments, the ionic liquid is 1-butyl-3-methylimidazoliumtetrafluoroborate.

In certain embodiments, the ionic liquid is 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide.

In certain embodiments, the ionic liquid is 1-ethyl-3-methylimidazoliumtetrafluoroborate.

In certain embodiments, the ionic liquid is 1-ethyl-3-methylimidazoliumtetracyanoborate.

In certain embodiments, the ionic liquid is 1-hexyl-3-methylimidazoliumtetracyanoborate.

In certain embodiments, the ionic liquid is1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide.

In one embodiment, the ionic liquid is 1-butyl-1-methylpyrrolidiniumtris(pentafluoroethyl)trifluorophosphate.

In certain embodiments, the ionic liquid is1-butyl-1-methylpyrrolidinium tetracyanoborate.

In certain embodiments, the ionic liquid istrihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide.

In certain embodiments, the ionic liquid is 1-butyl-1-methylpiperidiniumbis(trifluoromethylsulfonyl)imide.

In certain embodiments, the ionic liquid is butyltrimethylammoniumbis(trifluoromethylsulfonyl)imide

In certain embodiments, the ionic liquid is 1-butyl-3-methylimidazoliumtrifluoromethanesulfonate.

In certain embodiments, the organic solvent is selected from ethylisopropyl sulfone, ethyl isobutyl sulfone, ethyl methyl sulfone, methylisopropyl sulfone, isopropyl isobutyl sulfone, isopropyl s-butylsulfone, butyl isobutyl sulfone, or bimethyl sulfone, linear sulfones.

In certain embodiments, the organic solvent is selected frompolypropylene carbonate, propylene carbonate, dimethyl carbonate,ethylene carbonate.

In certain embodiments, the organic solvent is acetonitrile.

In certain embodiments, the enhanced electrolyte composition is an ionicliquid with an organic solvent, wherein the organic solvent is 55%-90%,e.g., 37.5%, by volume of the composition.

In certain embodiments, the enhanced electrolyte composition is an ionicliquid with a second ionic liquid, wherein one ionic liquid is 5%>-90%>,e.g., 60%>, by volume of the composition.

The enhanced electrolyte combinations of the present invention provide awider temperature range performance for an individual capacitor {e.g.without a significant drop in capacitance and/or increase in ESR whentransitioning between two temperatures, e.g. without more than a 90%decrease in capacitance and/or a 1000% increase in ESR whentransitioning from about +30° C. to about −40° C.), and increasedtemperature durability for an individual capacitor {e.g., less than a50% decrease in capacitance at a given temperature after a given timeand/or less than a 100% increase in ESR at a given temperature after agiven time, and/or less than 10 A/L of leakage current at a giventemperature after a given time, e.g., less than a 40%> decrease incapacitance and/or a 75% increase in ESR, and/or less than 5 A/L ofleakage current, e.g., less than a 30% decrease in capacitance and/or a50% increase in ESR, and/or less than 1 A/L of leakage current).

Without wishing to be bound by theory, the combinations described aboveprovide enhanced eutectic properties that affect the freezing point ofthe advanced electrolyte system to afford ultracapacitors that operatewithin performance and durability standards at temperatures of down to−40 degrees Celsius.

As described above for the novel electrolytes of the present invention,in certain embodiments, the advanced electrolyte system (AES) may beadmixed with electrolytes provided that such combination does notsignificantly affect the advantages achieved by utilization of theadvanced electrolyte system.

In certain embodiments, the enhanced electrolyte combinations areselected herein for use the advanced electrolyte systems may also bepurified. Such purification may be performed using art-recognizedtechniques or techniques provided herein.

Referring now to FIG. 8, there are shown various additional embodimentsof cations 9 suited for use in an ionic liquid to provide theelectrolyte 6. These cations 9 may be used alone or in combination witheach other, in combination with at least some of the foregoingembodiments of cations 9, and may also be used in combination with othercations 9 that are deemed compatible and appropriate by a user,designer, manufacturer or other similarly interested party. The cations9 depicted in FIG. 8 include, without limitation, ammonium, imidazolium,oxazolium, phosphonium, piperidinium, pyrazinium, pyrazinium,pyridazinium, pyridinium, pyrimidinium, pyrrolidinium, sulfonium,thiazolium, triazolium, guanidium, isoquinolinium, benzotriazolium,viologen-types, and functionalized imidazolium cations.

With regard to the cations 9 shown in FIG. 8, various branch groups(R_(1s), R₂, R₃, . . . R_(X)) are included. In the case of the cations9, each branch groups (R_(x)) may be one of alkyl, heteroalkyl, alkenyl,heteroalkenyl, alkynyl, heteroalkynyl, halo, amino, nitro, cyano,hydroxyl, sulfate, sulfonate, or a carbonyl group any of which isoptionally substituted.

The term “alkyl” is recognized in the art and may include saturatedaliphatic groups, including straight-chain alkyl groups, branched-chainalkyl groups, cycloalkyl (alicyclic) groups, alkyl substitutedcycloalkyl groups, and cycloalkyl substituted alkyl groups. In certainembodiments, a straight chain or branched chain alkyl has about 20 orfewer carbon atoms in its backbone (e.g., C₁-C₂₀ for straight chain,C₁-C₂₀ for branched chain). Likewise, cycloalkyls have from about 3 toabout 10 carbon atoms in their ring structure, and alternatively about5, 6 or 7 carbons in the ring structure. Examples of alkyl groupsinclude, but are not limited to, methyl, ethyl, propyl, butyl, pentyl,hexyl, ethyl hexyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl andthe like.

The term “heteroalkyl” is recognized in the art and refers to alkylgroups as described herein in which one or more atoms is a heteroatom(e.g., oxygen, nitrogen, sulfur, and the like). For example, alkoxygroup (e.g., —OR) is a heteroalkyl group.

The terms “alkenyl” and “alkynyl” are recognized in the art and refer tounsaturated aliphatic groups analogous in length and possiblesubstitution to the alkyls described above, but that contain at leastone double or triple bond respectively.

The “heteroalkenyl” and “heteroalkynyl” are recognized in the art andrefer to alkenyl and alkynyl alkyl groups as described herein in whichone or more atoms is a heteroatom (e.g., oxygen, nitrogen, sulfur, andthe like).

Generally, any ion with a negative charge maybe used as the anion 11.The anion 11 selected is generally paired with a large organic cation 9to form a low temperature melting ionic salt. Room temperature (andlower) melting salts come from mainly large anions 9 with a charge of−1. Salts that melt at even lower temperatures generally are realizedwith anions 11 with easily delocalized electrons. Anything that willdecrease the affinity between ions (distance, delocalization of charge)will subsequently decrease the melting point. Although possible anionformations are virtually infinite, only a subset of these will work inlow temperature ionic liquid application. This is a non-limitingoverview of possible anion formations for ionic liquids.

Common substitute groups (a) suited for use of the anions 11 provided inTable 3 include: —F, —Cl″, —Br″, —I⁻—OCH₃″, —CN″, —SCN″, —C₂H₃O₂″,—ClO″, —ClO₂″, —ClO₃″, —ClO₄″, —NCO″, —NCS″, —NCSe″, —NCN″, —OCH(CH₃)₂″,—CH₂OCH₃″, —COOH″, —OH″, —SOCH₃″, —SO₂CH₃″, —SOCH₃″, —SO₂CF₃″, —SO₃H″,—SO₃CF₃″, —O(CF₃)₂C₂(CF₃)₂O″, —CF₃″, —CHF₂″, —CH₂F″, —CH₃″—NO₃″, —NO₂″,—SO₃″, —SO₄ ²″, —SF₅″, —CB_(n)H₁₂″, —CB_(n)H₆Ci₆″, —CH₃CB_(n)H_(n)″,—C₂H₅CB_(ii)H_(ii)″, -A-PO₄″, -A-SO₂″, A-SO₃″, -A-SO₃H″, -A-COO″, -A-CO″{where A is a phenyl (the phenyl group or phenyl ring is a cyclic groupof atoms with the formula CeH₅) or substituted phenyl, alkyl, (a radicalthat has the general formula CnH_(2n)+i, formed by removing a hydrogenatom from an alkane) or substituted alkyl group, negatively chargedradical alkanes, (alkane are chemical compounds that consist only ofhydrogen and carbon atoms and are bonded exclusively by single bonds)halogenated alkanes and ethers (which are a class of organic compoundsthat contain an oxygen atom connected to two alkyl or aryl groups).

With regard to anions 11 suited for use in an ionic liquid that providesthe electrolyte 6, various organic anions 11 may be used. Exemplaryanions 11 and structures thereof are provided in Table 3. In a firstembodiment, (No. 1), exemplary anions 11 are formulated from the list ofsubstitute groups (a) provided above, or their equivalent. In additionalembodiments, (Nos. 2-5), exemplary anions 11 are formulated from arespective base structure (Y₂, Y₃, Y₄, . . . Y_(n)) and a respectivenumber of anion substitute groups (a_(1s) a₂, a₃, . . . a_(n)), wherethe respective number of anion substitute groups (a) may be selectedfrom the list of substitute (a) groups provided above, or theirequivalent. Note that in some embodiments, a plurality of anionsubstitute groups (a) (i.e., at least one differing anion substitutegroup (a)) may be used in any one embodiment of the anion 11. Also, notethat in some embodiments, the base structure (Y) is a single atom or adesignated molecule (as described in Table 3), or may be an equivalent.

More specifically, and by way of example, with regard to the exemplaryanions provided in Table 3, certain combinations may be realized. As oneexample, in the case of No. 2, the base structure (Y₂) includes a singlestructure (e.g., an atom, or a molecule) that is bonded to two anionsubstitute groups (a₂). While shown as having two identical anionsubstitute groups (a₂), this need not be the case. That is, the basestructure (Y₂) may be bonded to varying anion substitute groups (a₂),such as any of the anion substitute groups (a) listed above. Similarly,the base structure (Y₃) includes a single structure (e.g., an atom) thatis bonded to three anion substitute groups (a₃), as shown in case No. 3.Again, each of the anion substitute groups (a) included in the anion maybe varied or diverse, and need not repeat (be repetitive or besymmetric) as shown in Table 3. In general, with regard to the notationin Table 3, a subscript on one of the base structures denotes a numberof bonds that the respective base structure may have with anionsubstitute groups (a). That is, the subscript on the respective basestructure (Y_(n)) denotes a number of accompanying anion substitutegroups (a_(n)) in the respective anion.

TABLE 3 Exemplary Organic Anions for an Ionic Liquid No.: Ion Guidelinesfor Anion Structure and Exemplary Ionic Liquids 1 -a_(i) Some of theabove a may mix with organic cations to form an ionic liquid. Anexemplary anion: Cl⁻ Exemplary ionic liquid: [BMI*][Cl] *BMI - butylmethyl immadizolium

2 -Y₂a₂ Y₂ may be any of the following: N, O, C═O, S═O. Exemplary anionsinclude: B (CF₃C0₂)₄ ⁻N(SO₂CF₃)₂ ⁻ Exemplary ionic liquid: [EMI*][NTF₂]*EMI - ethyl methyl immadizolium

3 -Y₃a₃ Y₃ may be any of the following: Be, C, N, O, Mg, Ca, Ba, Ra, Au.Exemplary anions include: —C(SO₂CF₃)₃ ⁻ Exemplary ionic liquid: [BMI]C(SO₂CF₃)₃ ⁻

4 -Y₄a₄ Y₄ may be any of the following: B, Al, Ga, Th, In, P. Exemplaryanions include: —BF₄ ⁻, —AlCl₄ ⁻ Exemplary ionic liquid: [BMI][BF₄]

5 -Y₆a₆ Y₆ can be any of the following: P, S, Sb, As, N, Bi, Nb, Sb.Exemplary anions include: —P(CF₃)₄F₂ ⁻, —AsF₆ ⁻ Exemplary ionic liquid:[BMI][PF₆]

The term “cyano” is given its ordinary meaning in the art and refers tothe group, CN. The term “sulfate” is given its ordinary meaning in theart and refers to the group, SO₂. The term “sulfonate” is given itsordinary meaning in the art and refers to the group, SO₃X, where X maybe an electron pair, hydrogen, alkyl or cycloalkyl. The term “carbonyl”is recognized in the art and refers to the group, C=0.

An important aspect for consideration in construction of theultracapacitor 10 is maintaining good chemical hygiene. In order toassure purity of the components, in various embodiments, the activatedcarbon, carbon fibers, rayon, carbon cloth, and/or nanotubes making upthe energy storage media 1 for the two electrodes 3, are dried atelevated temperature in a vacuum environment. The separator 5 is alsodried at elevated temperature in a vacuum environment. Once theelectrodes 3 and the separator 5 are dried under vacuum, they arepackaged in the housing 7 without a final seal or cap in an atmospherewith less than 50 parts per million (ppm) of water. The uncappedultracapacitor 10 may be dried, for example, under vacuum over atemperature range of about 100 degrees Celsius to about 250 degreesCelsius. Once this final drying is complete, the electrolyte 6 may beadded and the housing 7 is sealed in a relatively dry atmosphere (suchas an atmosphere with less than about 50 ppm of moisture). Of course,other methods of assembly may be used, and the foregoing provides merelya few exemplary aspects of assembly of the ultracapacitor 10.

Generally, impurities in the electrolyte 6 are kept to a minimum. Forexample, in some embodiments, a total concentration of halide ions(chloride, bromide, fluoride, iodide), is kept to below about 1,000 ppm.A total concentration of metallic species (e.g., Br, Cd, Co, Cr, Cu, Fe,K, Li, Mo, Na, Ni, Pb, Zn, including an at least one of an alloy and anoxide thereof), is kept to below about 1,000 ppm. Further, impuritiesfrom solvents and precursors used in the synthesis process are keptbelow about 1,000 ppm and can include, for example, bromoethane,chloroethane, 1-bromobutane, 1-chlorobutane, 1-methylimidazole, ethylacetate, methylene chloride and so forth.

In some embodiments, the impurity content of the ultracapacitor 10 hasbeen measured using ion selective electrodes and the Karl Fischertitration procedure, which has been applied to electrolyte 6 of theultracapacitor 10. It has been found that the total halide content inthe ultracapacitor 10 according to the teachings herein has been foundto be less than about 200 ppm of halides (Cr and F″) and water contentis less than about 100 ppm.

One example of a technique for purifying electrolyte is provided in areference entitled “The oxidation of alcohols in substituted imidazoliumionic liquids using ruthenium catalysts,” Farmer and Welton, The RoyalSociety of Chemistry, 2002, 4, 97-102. An exemplary process is alsoprovided herein.

The advanced electrolyte systems (AES) of the present inventioncomprise, in some embodiments, certain novel electrolytes for use inhigh temperature ultracapacitors. In this respect, it has been foundthat maintaining purity and low moisture relates to a degree ofperformance of the energy storage 10; and that the use of electrolytesthat contain hydrophobic materials and which have been found todemonstrate greater purity and lower moisture content are advantageousfor obtaining improved performance. These electrolytes exhibit goodperformance characteristics in a temperature range of about minus 40degrees Celsius to about 250 degrees Celsius, e.g., about minus 10degrees Celsius to about 250 degrees Celsius, e.g., about minus 5degrees Celsius to about 250 degrees Celsius e.g., about 0 degreesCelsius to about 250 degrees Celsius e.g., about minus 20 degreesCelsius to about 200 degrees Celsius e.g., about 150 degrees Celsius toabout 250 degrees Celsius e.g., about 150 degrees Celsius to about 220degrees Celsius e.g., about 150 degrees Celsius to about 200 degreesCelsius, e.g., about minus 10 degrees Celsius to about 210 degreesCelsius e.g., about minus 10 degrees Celsius to about 220 degreesCelsius e.g., about minus 10 degrees Celsius to about 230 degreesCelsius.

Accordingly, novel electrolyte entities useful as the advancedelectrolyte system (AES) include species comprising a cation (e.g.,cations shown in FIG. 8 and described herein) and an anion, orcombinations of such species. In some embodiments, the species comprisesa nitrogen-containing, oxygen-containing, phosphorus-containing, and/orsulfur-containing cation, including heteroaryl and heterocyclic cations.In one set of embodiments, the advanced electrolyte system (AES) includespecies comprising a cation selected from the group consisting ofammonium, imidazolium, oxazolium, phosphonium, piperidinium, pyrazinium,pyrazolium, pyridazinium, pyridinium, pyrimidinium, sulfonium,thiazolium, triazolium, guanidium, isoquinolinium, benzotriazolium, andviologen-type cations, any of which may be substituted with substituentsas described herein. In one embodiment, the novel electrolyte entitiesuseful for the advanced electrolyte system (AES) of the presentinvention include any combination of cations presented in FIG. 8,selected from the group consisting of phosphonium, piperidinium, andammonium, wherein the various branch groups Rx (e.g., Ri, R2, R3, . . .−Rx) may be selected from the group consisting of alkyl, heteroalkyl,alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, halo, amino, nitro,cyano, hydroxyl, sulfate, sulfonate, and carbonyl, any of which isoptionally substituted, and wherein at least two Rx are not H (i.e.,such that the selection and orientation of the R groups produce thecationic species shown in FIG. 8); and the anion selected from the groupconsisting of tetrafluoroborate, bis(trifluoromethylsulfonyl)imide,tetracyanoborate, and trifluoromethanesulfonate.

For example, given the combinations of cations and anions above, in aparticular embodiment, the AES may be selected from the group consistingof trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide,1-butyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)imide, andbutyltrimethylammonium bis(trifluoromethylsulfonyl)imide.

In certain embodiments, the AES is trihexyltetradecylphosphoniumbis(trifluoromethylsulfonyl)imide.

In certain embodiments, the AES is 1-butyl-1-methylpiperidiniumbis(trifluoromethylsulfonyl)imide.

In certain embodiments, the AES is butyltrimethylammoniumbis(trifluoromethylsulfonyl)imide.

In another embodiment, the novel electrolyte entities useful for theadvanced electrolyte system (AES) of the present invention include anycombination of cations presented in FIG. 8, selected from the groupconsisting of imidazolium and pyrrolidinium, wherein the various branchgroups Rx (e.g., Ri, R2, R3, . . . Rx) may be selected from the groupconsisting of alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl,heteroalkynyl, halo, amino, nitro, cyano, hydroxyl, sulfate, sulfonate,and carbonyl, any of which is optionally substituted, and wherein atleast two Rx are not H (i.e., such that the selection and orientation ofthe R groups produce the cationic species shown in FIG. 8); and theanion selected from the group consisting of tetrafluoroborate,bis(trifluoromethylsulfonyl)imide, tetracyanoborate, andtrifluoromethanesulfonate. In one particular embodiment, the two Rx thatare not H, are alkyl. Moreover, the noted cations exhibit high thermalstability, as well as high conductivity and exhibit good electrochemicalperformance over a wide range of temperatures.

For example, given the combinations of cations and anions above, in aparticular embodiment, the AES may be selected from the group consistingof 1-butyl-3-methylimidazolium tetrafluoroborate;1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide,1-ethyl-3-methylimidazolium tetrafluoroborate;1-ethyl-3-methylimidazolium tetracyanoborate;1-hexyl-3-methylimidazolium tetracyanoborate;1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide;1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate;1-butyl-1-methylpyrrolidinium tetracyanoborate, and1-butyl-3-methylimidazolium trifluoromethanesulfonate.

In one embodiment, the AES is 1-butyl-3-methylimidazoliumtetrafluoroborate

In one embodiment, the AES is 1-butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide.

In one embodiment, the AES is 1-ethyl-3-methylimidazoliumtetrafluoroborate.

In one embodiment, the AES is 1-ethyl-3-methylimidazoliumtetracyanoborate.

In one embodiment, the AES is 1-hexyl-3-methylimidazoliumtetracyanoborate.

In one embodiment, the AES is 1-butyl-1-methylpyrrolidiniumbis(trifluoromethylsulfonyl)imide.

In one embodiment, the AES is 1-butyl-1-methylpyrrolidiniumtris(pentafluoroethyl)trifluorophosphate.

In one embodiment, the AES is 1-butyl-1-methylpyrrolidiniumtetracyanoborate.

In one embodiment, the AES is 1-butyl-3-methylimidazoliumtrifluoromethanesulfonate.

In another particular embodiment, one of the two Rx that are not H, isalkyl, e.g., methyl, and the other is an alkyl substituted with analkoxy. Moreover, it has been found that cations having an N,O-acetalskeleton structure of the formula (1) in the molecule have highelectrical conductivity, and that an ammonium cation included amongthese cations and having a pyrrolidine skeleton and an N,O-acetal groupis especially high in electrical conductivity and solubility in organicsolvents and supports relatively high voltage. As such, in oneembodiment, the advanced electrolyte system comprises a salt of thefollowing formula:

wherein R1 and R2 can be the same or different and are each alkyl, andX− is an anion. In some embodiments, Ri is straight-chain or branchedalkyl having 1 to 4 carbon atoms, R2 is methyl or ethyl, and X″ is acyanoborate-containing anion 11. In a specific embodiment, X″ comprises[B(CN)]4 and R2 is one of a methyl and an ethyl group. In anotherspecific embodiment, Ri and R2 are both methyl. In addition, in oneembodiment, cyanoborate anions 11, X″ suited for the advancedelectrolyte system of the present invention include, [B(CN)4]˜ or[BFn(CN)4−n]˜, where n=0, 1, 2 or 3.

Examples of cations of the AES of the present invention comprising aNovel Electrolyte Entity of formula (1), and which are composed of aquaternary ammonium cation shown in formula (I) and a cyanoborate anionare selected from N-methyl-N-methoxymethylpyrrolidinium(N-methoxymethyl-N-methylpyrrolidinium),N-ethyl-N-methoxymethylpyrrolidinium,N-methoxymethyl-N-n-propylpyrrolidinium,N-methoxymethyl-N-iso-propylpyrrolidinium,N-n-butyl-N-methoxymethylpyrrolidinium,N-iso-butyl-N-methoxymethylpyrrolidinium,N-tert-butyl-N-methoxymethylpyrrolidinium,N-ethoxymethyl-N-methylpyrrolidinium,N-ethyl-N-ethoxymethylpyrrolidinium(N-ethoxymethyl-N-ethylpyrrolidinium),N-ethoxymethyl-N-n-propylpyrrolidinium,N-ethoxymethyl-N-iso-propylpyrrolidinium,N-n-butyl-N-ethoxymethylpyrrolidinium,N-iso-butyl-N-ethoxymethylpyrrolidinium andN-tert-butyl-N-ethoxymethylpyrrolidinium. Other examples includeN-methyl-N-methoxymethylpyrrolidinium(N-methoxymethyl-N-methylpyrrolidinium),N-ethyl-N-methoxymethylpyrrolidinium andN-ethoxymethyl-N-methylpyrrolidinium.

Additional examples of the cation of formula (1) in combination withadditional anions may be selected fromN-methyl-N-methoxymethylpyrrolidinium tetracyanoborate(N-methoxymethyl-N-methylpyrrolidinium tetracyanoborate),N-ethyl-N-methoxymethylpyrrolidinium tetracyanoborate,N-ethoxymethyl-N-methylpyrrolidinium tetracyanoborate,N-methyl-N-methoxymethylpyrrolidinium bistrifluoromethanesulfonylimide,(N-methoxymethyl-N-methylpyrrolidiniumbistrifluoromethanesulfonylimide), N-ethyl-N-methoxymethylpyrrolidiniumbistrifluoromethanesulfonylimide, N-ethoxymethyl-N-methylpyrrolidiniumbistrifluoromethanesulfonylimide, N-methyl-N-methoxymethylpyrrolidiniumtrifluoromethanesulfolate(N-methoxymethyl-N-methyltrifluoromethanesulfolate).

When to be used as an electrolyte, the quaternary ammonium salt may beused as admixed with a suitable organic solvent. Useful solvents includecyclic carbonic acid esters, chain carbonic acid esters, phosphoric acidesters, cyclic ethers, chain ethers, lactone compounds, chain esters,nitrile compounds, amide compounds and sulfone compounds. Examples ofsuch compounds are given below although the solvents to be used are notlimited to these compounds.

Examples of cyclic carbonic acid esters are ethylene carbonate,propylene carbonate, butylene carbonate and the like, among whichpropylene carbonate is preferable.

Examples of chain carbonic acid esters are dimethyl carbonate,ethylmethyl carbonate, diethyl carbonate and the like, among whichdimethyl carbonate and ethylmethyl carbonate are preferred.

Examples of phosphoric acid esters are trimethyl phosphate, triethylphosphate, ethyldimethyl phosphate, diethylmethyl phosphate and thelike. Examples of cyclic ethers are tetrahydrofuran,2-methyltetrahydrofuran and the like. Examples of chain ethers aredimethoxy ethane and the like. Examples of lactone compounds areγ-butyrolactone and the like. Examples of chain esters are methylpropionate, methyl acetate, ethyl acetate, methyl formate and the like.Examples of nitrile compounds are acetonitrile and the like. Examples ofamide compounds are dimethylformamide and the like. Examples of sulfonecompounds are sulfolane, methyl sulfolane and the like. Cyclic carbonicacid esters, chain carbonic acid esters, nitrile compounds and sulfonecompounds may be particularly desirable, in some embodiments.

These solvents may be used singly, or at least two kinds of solvents maybe used in admixture. Examples of preferred organic solvent mixtures aremixtures of cyclic carbonic acid ester and chain carbonic acid estersuch as those of ethylene carbonate and dimethyl carbonate, ethylenecarbonate and ethylmethyl carbonate, ethylene carbonate and diethylcarbonate, propylene carbonate and dimethyl carbonate, propylenecarbonate and ethylmethyl carbonate and propylene carbonate and diethylcarbonate, mixtures of chain carbonic acid esters such as dimethylcarbonate and ethylmethyl carbonate, and mixtures of sulfolane compoundssuch as sulfolane and methylsulfolane. More preferable are mixtures ofethylene carbonate and ethylmethyl carbonate, propylene carbonate andethylmethyl carbonate, and dimethyl carbonate and ethylmethyl carbonate.

In some embodiments, when the quaternary ammonium salt of the inventionis to be used as an electrolyte, the electrolyte concentration is atleast 0.1 M, in some cases at least 0.5 M and may be at least 1 M. Ifthe concentration is less than 0.1 M, low electrical conductivity willresult, producing electrochemical devices of impaired performance. Theupper limit concentration is a separation concentration when theelectrolyte is a liquid salt at room temperature. When the solution doesnot separate, the limit concentration is 100%. When the salt is solid atroom temperature, the limit concentration is the concentration at whichthe solution is saturated with the salt.

In certain embodiments, the advanced electrolyte system (AES) may beadmixed with electrolytes other than those disclosed herein providedthat such combination does not significantly affect the advantagesachieved by utilization of the advanced electrolyte system, e.g., byaltering the performance or durability characteristics by greater than10%. Examples of electrolytes that may be suited to be admixed with theAES are alkali metal salts, quaternary ammonium salts, quaternaryphosphonium salts, etc. These electrolytes may be used singly, or atleast two kinds of them are usable in combination, as admixed with theAES disclosed herein. Useful alkali metal salts include lithium salts,sodium salts and potassium salts. Examples of such lithium salts arelithium hexafluorophosphate, lithium borofluoride, lithium perchlorate,lithium trifluoromethanesulfonate, sulfonylimide lithium,sulfonylmethide lithium and the like, which nevertheless are notlimitative. Examples of useful sodium salts are sodiumhexafluorophosphate, sodium borofluoride, sodium perchlorate, sodiumtrifluoromethanesulfonate, sulfonylimide sodium, sulfonylmethide sodiumand the like. Examples of useful potassium salts are potassiumhexafluorophosphate, potassium borofluoride, potassium perchlorate,potassium trifluoromethanesulfonate, sulfonylimide potassium,sulfonylmethide potassium and the like although these are notlimitative.

Useful quaternary ammonium salts that may be used in the combinationsdescribed above (i.e., which do not significantly affect the advantagesachieved by utilization of the advanced electrolyte system) includetetraalkylammonium salts, imidazolium salts, pyrazolium salts,pyridinium salts, triazolium salts, pyridazinium salts, etc., which arenot limitative. Examples of useful tetraalkylammonium salts aretetraethylammonium tetracyanoborate, tetramethylammoniumtetracyanoborate, tetrapropylammonium tetracyanoborate,tetrabutylammonium tetracyanoborate, triethylmethylammoniumtetracyanoborate, trimethylethylammonium tetracyanoborate,dimethyldiethylammonium tetracyanoborate, trimethylpropylammoniumtetracyanoborate, trimethylbutylammonium tetracyanoborate,dimethylethylpropylammonium tetracyanoborate,methylethylpropylbutylammonium tetracyanoborate,N,N-dimethylpyrrolidinium tetracyanoborate,N-ethyl-N-methylpyrrolidinium tetracyanoborate,N-methyl-N-propylpyrrolidinium tetracyanoborate,N-ethyl-N-propylpyrrolidinium tetracyanoborate, N,N-dimethylpiperidiniumtetracyanoborate, N-methyl-N-ethylpiperidinium tetracyanoborate,N-methyl-N-propylpiperidinium tetracyanoborate,N-ethyl-N-propylpiperidinium tetracyanoborate, N,N-dimethylmorpholiniumtetracyanoborate, N-methyl-N-ethylmorpholinium tetracyanoborate,N-methyl-N-propylmorpholinium tetracyanoborate,N-ethyl-N-propylmorpholinium tetracyanoborate and the like, whereasthese examples are not limitative.

Examples of imidazolium salts that may be used in the combinationsdescribed above (i.e., which do not significantly affect the advantagesachieved by utilization of the advanced electrolyte system) include1,3-dimethylimidazolium tetracyanoborate, 1-ethyl-3-methylimidazoliumtetracyanoborate, 1,3-diethylimidazolium tetracyanoborate,1,2-dimethyl-3-ethylimidazolium tetracyanoborate and1,2-dimethyl-3-propylimidazolium tetracyanoborate, but are not limitedto these. Examples of pyrazolium salts are 1,2-dimethylpyrazoliumtetracyanoborate, 1-methyl-2-ethylpyrazolium tetracyanoborate,1-propyl-2-methylpyrazolium tetracyanoborate and1-methyl-2-butylpyrazolium tetracyanoborate, but are not limited tothese. Examples of pyridinium salts are N-methylpyridiniumtetracyanoborate, N-ethylpyridinium tetracyanoborate, N-propylpyridiniumtetracyanoborate and N-butylpyridinium tetracyanoborate, but are notlimited to these. Examples of triazolium salts are 1-methyltriazoliumtetracyanoborate, 1-ethyltriazolium tetracyanoborate, 1-propyltriazoliumtetracyanoborate and 1-butyltriazolium tetracyanoborate, but are notlimited to these. Examples of pyridazinium salts are1-methylpyridazinium tetracyanoborate, 1-ethylpyridaziniumtetracyanoborate, 1-propylpyridazinium tetracyanoborate and1-butylpyridazinium tetracyanoborate, but are not limited to these.Examples of quaternary phosphonium salts are tetraethylphosphoniumtetracyanoborate, tetramethylphosphonium tetracyanoborate,tetrapropylphosphonium tetracyanoborate, tetrabutylphosphoniumtetracyanoborate, triethylmethylphosphonium tetrafluoroborate,trimethylethylphosphonium tetracyanoborate, dimethyldiethylphosphoniumtetracyanoborate, trimethylpropylphosphonium tetracyanoborate,trimethylbutylphosphonium tetracyanoborate,dimethylethylpropylphosphonium tetracyanoborate,methylethylpropylbutylphosphonium tetracyanoborate, but are not limitedto these.

Exemplary High Temperature Solid State Electrolyte

Disclosed herein is an energy storage device, e.g., a device comprisingan EDLC that provides users with improved performance in a wide range oftemperatures. For example, the energy storage device may be operable attemperatures ranging from as low as 0 C (degrees Celsius) or even below,to as high as about 300 C or more. In some embodiments, the energystorage device is operable at temperatures as high as about 200 C, 210C, 220, C, 230 C, 240 C, 250 C, 260 C, 270 C, 280 C, 290 C, 300 C, ormore and, in some embodiments, as low as 0 C or below. In someembodiments, the ultracapacitors may be configured to survivetemperatures out side of the operating temperature range when notoperating (e.g., maintained in a discharged state). For example, in someembodiments, the ultracapacitor may survive temperatures of up to 310 Cor more and/or below 0 C, −10 C, −20, C, −30 C, −40 C, −45 C, −50 C, −55C or less. In some embodiments, the ultracapacitor may be configured tohave an operating temperature range of 0 C to 300 C, or any sub-rangethereof, and/or a survivability temperature range of −55 C to 310 C, orany sub-range thereof.

In general, the device includes energy storage media that is adapted forproviding high power density and high energy density when compared toprior art devices. The device includes components that are configuredfor ensuring operation over the temperature range, and includes any oneor more of a variety of forms of electrolyte that are likewise rated forthe temperature range. The combination of construction, energy storagemedia and electrolyte result in capabilities to provide robust operationunder extreme conditions. To provide some perspective, aspects of anexemplary embodiment are now introduced.

As shown in FIGS. 1A and 1B, exemplary embodiments of a capacitor areshown. In each case, the capacitor is an “ultracapacitor 10.” Thedifference between FIG. 1A and FIG. 1B is the inclusion of a separatorin exemplary ultracapacitor 10 of FIG. 1A. The concepts disclosed hereingenerally apply equally to any exemplary ultracapacitor 10. Certainelectrolytes of certain embodiments are uniquely suited to constructingan exemplary ultracapacitor 10 without a separator. Unless otherwisenoted, the discussion herein applies equally to any ultracapacitor 10,with or without a separator.

The exemplary ultracapacitor 10 is an electric double-layer capacitor(EDLC). The EDLC includes at least one pair of electrodes 3 (where theelectrodes 3 may be referred to as a negative electrode 3 and a positiveelectrode 3, merely for purposes of referencing herein). When assembledinto the ultracapacitor 10, each of the electrodes 3 presents a doublelayer of charge at an electrolyte interface. In some embodiments, aplurality of electrodes 3 is included (for example, in some embodiments,at least two pairs of electrodes 3 are included). However, for purposesof discussion, only one pair of electrodes 3 are shown. As a matter ofconvention herein, at least one of the electrodes 3 uses a carbon-basedenergy storage media 1 (as discussed further herein) to provide energystorage. However, for purposes of discussion herein, it is generallyassumed that each of the electrodes includes the carbon-based energystorage media 1. It should be noted that an electrolytic capacitordiffers from an ultracapacitor because, among other things, metallicelectrodes differ greatly (at least an order of magnitude) in surfacearea.

Each of the electrodes 3 includes a respective current collector 2 (alsoreferred to as a “charge collector”). In some embodiments, theelectrodes 3 are separated by a separator 5. In general, the separator 5is a thin structural material (usually a sheet) used to separate thenegative electrode 3 from the positive electrode 3. The separator 5 mayalso serve to separate pairs of the electrodes 3. Once assembled, theelectrodes 3 and the separator 5 provide a storage cell 12. Note that,in some embodiments, the carbon-based energy storage media 1 may not beincluded on one or both of the electrodes 3. That is, in someembodiments, a respective electrode 3 might consist of only the currentcollector 2. The material used to provide the current collector 2 couldbe roughened, anodized or the like to increase a surface area thereof.In these embodiments, the current collector 2 alone may serve as theelectrode 3. With this in mind, however, as used herein, the term“electrode 3” generally refers to a combination of the energy storagemedia 1 and the current collector 2 (but this is not limiting, for atleast the foregoing reason).

At least one form of electrolyte 6 is included in the ultracapacitor 10.The electrolyte 6 fills void spaces in and between the electrodes 3 andthe separator 5. In general, the electrolyte 6 is a substance thatdisassociates into electrically charged ions. A solvent that dissolvesthe substance may be included in some embodiments of the electrolyte 6,as appropriate. The electrolyte 6 conducts electricity by ionictransport.

Generally, the storage cell 12 is formed into one of a wound form orprismatic form which is then packaged into a cylindrical or prismatichousing 7. Once the electrolyte 6 has been included, the housing 7 maybe hermetically sealed. In various examples, the package is hermeticallysealed by techniques making use of laser, ultrasonic, and/or weldingtechnologies. In addition to providing robust physical protection of thestorage cell 12, the housing 7 is configured with external contacts toprovide electrical communication with respective terminals 8 within thehousing 7. Each of the terminals 8, in turn, provides electrical accessto energy stored in the energy storage media 1, generally throughelectrical leads which are coupled to the energy storage media 1.

Consider now the energy storage media 1 in greater detail. In theexemplary ultracapacitor 10, the energy storage media 1 is formed ofcarbon nanotubes. The energy storage media 1 may include othercarbonaceous materials including, for example, activated carbon, carbonfibers, rayon, graphene, aerogel, carbon cloth, and a plurality of formsof carbon nanotubes. Activated carbon electrodes can be manufactured,for example, by producing a carbon base material by carrying out a firstactivation treatment to a carbon material obtained by carbonization of acarbon compound, producing a formed body by adding a binder to thecarbon base material, carbonizing the formed body, and finally producingan active carbon electrode by carrying out a second activation treatmentto the carbonized formed body. Carbon fiber electrodes can be produced,for example, by using paper or cloth pre-form with high surface areacarbon fibers.

In some embodiments, the electrode of the ultracapacitor 10 includes acurrent collector comprising aluminum with an aluminum carbide layer onat least one surface, on which at least one layer of carbon nanotubes(CNTs) is disposed. The electrode may comprise vertically-aligned,horizontally-aligned, or nonaligned (e.g., tangled or clustered) CNTs.The electrode may comprise compressed CNTs. The electrode may comprisesingle-walled, double-walled, or multiwalled CNTs. The electrode maycomprise multiple layers of CNTs. In some embodiments, the carbide layerincludes elongated whisker structures with a nanoscale width. In someembodiments, the whiskers protrude into the layer of CNTs. In someembodiments, the whiskers protrude through an intervening layer (e.g.,an oxide layer) into the layer of CNTs. Further details relating toelectrodes of this type may be found in U.S. Provisional PatentApplication No. 62/061,947 “ELECTRODE FOR ENERGY STORAGE DEVICE USINGANODIZED ALUMINUM” filed Oct. 9, 2014, the entire contents of which areincorporated herein by reference.

In an exemplary method for fabricating carbon nanotubes, an apparatusfor producing an aligned carbon-nanotube aggregate includes apparatusfor synthesizing the aligned carbon-nanotube aggregate on a basematerial having a catalyst on a surface thereof. The apparatus includesa formation unit that processes a formation step of causing anenvironment surrounding the catalyst to be an environment of a reducinggas and heating at least either the catalyst or the reducing gas; agrowth unit that processes a growth step of synthesizing the alignedcarbon-nanotube aggregate by causing the environment surrounding thecatalyst to be an environment of a raw material gas and by heating atleast either the catalyst or the raw material gas; and a transfer unitthat transfers the base material at least from the formation unit to thegrowth unit. A variety of other methods and apparatus may be employed toprovide the aligned carbon-nanotube aggregate.

In some embodiments, material used to form the energy storage media 1may include material other than pure carbon (and the various forms ofcarbon as may presently exist or be later devised). That is, variousformulations of other materials may be included in the energy storagemedia 1. More specifically, and as a non-limiting example, at least onebinder material may be used in the energy storage media 1, however, thisis not to suggest or require addition of other materials (such as thebinder material). In general, however, the energy storage media 1 issubstantially formed of carbon, and may therefore referred to herein asa “carbonaceous material,” as a “carbonaceous layer” and by othersimilar terms. In short, although formed predominantly of carbon, theenergy storage media 1 may include any form of carbon (as well as anyadditives or impurities as deemed appropriate or acceptable) to providefor desired functionality as energy storage media 1.

In one set of embodiments, the carbonaceous material includes at leastabout 60% elemental carbon by mass, and in other embodiments at leastabout 75%, 85%, 90%, 95% or 98% by mass elemental carbon.

Carbonaceous material can include carbon in a variety forms, includingcarbon black, graphite, and others. The carbonaceous material caninclude carbon particles, including nanoparticles, such as nanotubes,nanorods, graphene sheets in sheet form, and/or formed into cones, rods,spheres (buckyballs) and the like.

Some embodiments of various forms of carbonaceous material suited foruse in energy storage media 1 are provided herein as examples. Theseembodiments provide robust energy storage and are well suited for use inthe electrode 3. It should be noted that these examples are illustrativeand are not limiting of embodiments of carbonaceous material suited foruse in energy storage media 1.

In general, the term “electrode” refers to an electrical conductor thatis used to make contact to another material which is often non-metallic,in a device that may be incorporated into an electrical circuit.Generally, the term “electrode,” as used herein, is with reference tothe current collector 2 and the additional components as may accompanythe current collector 2 (such as the energy storage media 1) to providefor desired functionality (for example, the energy storage media 1 whichis mated to the current collector 2 to provide for energy storage andenergy transmission). An exemplary process for complimenting the energystorage media 1 with the current collector 2 to provide the electrode 3is now provided.

The separator 5 may be fabricated from various materials. In someembodiments, the separator 5 is non-woven glass. The separator 5 mayalso be fabricated from fiberglass, ceramics and flouro-polymers, suchas polytetrafluoroethylene (PTFE), commonly marketed as TEFLON′ byDuPont Chemicals of Wilmington, Del. For example, using non-woven glass,the separator 5 can include main fibers and binder fibers each having afiber diameter smaller than that of each of the main fibers and allowingthe main fibers to be bonded together.

For longevity of the ultracapacitor 10 and to assure performance at hightemperature, the separator 5 should have a reduced amount of impuritiesand in particular, a very limited amount of moisture contained therein.In particular, it has been found that a limitation of about 200 ppm ofmoisture is desired to reduce chemical reactions and improve thelifetime of the ultracapacitor 10, and to provide for good performancein high temperature applications. Some embodiments of materials for usein the separator 5 include polyamide, polytetrafluoroethylene (PTFE),polyether-ether-ketone (PEEK), aluminum oxide (Al₂O₃), fiberglass,glass-reinforced plastic (GRP), polyester, nylon, and polyphenylenesulfide (PPS).

In general, materials used for the separator 5 are chosen according tomoisture content, porosity, melting point, impurity content, resultingelectrical performance, thickness, cost, availability and the like. Insome embodiments, the separator 5 is formed of hydrophobic materials.

Note that, in some embodiments, the ultracapacitor 10 does not requireor include the separator 5. For example, in some embodiments, such aswhere the electrodes 3 are assured of physical separation by a geometryof construction, it suffices to have electrolyte 6 alone between theelectrodes 3. More specifically, and as an example of physicalseparation, one such ultracapacitor 10 may include electrodes 3 that aredisposed within a housing such that separation is assured on acontinuous basis. For example, in embodiments described herein using asolid state polymer electrolyte doped with a ionic liquid, theelectrolyte itself may maintain mechanical separation of the electrodes3.

As described in detail above, the electrolyte 6 may include a pairing ofcations 9 and anions 11 and may include a solvent or other additives.The electrolyte 6 may include an “ionic liquid” as appropriate. Variouscombinations of cations 9, anions 11 and solvent may be used.

In some embodiments, the electrolyte 6 may be adapted such that theultracapacitor 10 is operable at temperatures as high as about 200 C,210 C, 220, C, 230 C, 240 C, 250 C, 260 C, 270 C, 280 C, 290 C, 300 C,310 C, 350 C or more and, in some embodiments, as low as 0 C or below.In some embodiments, the ultracapacitor 10 may be configured to survivetemperatures outside of its operating temperature range when notoperating (e.g., maintained in a discharged state). For example, in someembodiments, the ultracapacitor 10 may survive temperatures of up to 350C or more and/or below 0 C, −10 C, −20, C, −30 C, −40 C, −45 C, −50 C,−55 C or less. In some embodiments, the ultracapacitor 10 may beconfigured to have an operating temperature range of 0 C to 350 C, orany sub-range thereof, and/or a survivability temperature range of −55 Cto 350 C, or any sub-range thereof.

For example, a in FIG. 9, in some embodiments the electrolyte 6 mayinclude a solid state polymer matrix doped with one or more ionicliquids (comprising cations 9 and anions 11). The polymer electrolytemay be cast over the energy storage media 1 (as shown purified carbonnanotubes pCNT disposed on a current collector such an etched aluminumfoil). The electrolyte provides mechanical separation between theelectrodes, obviating the need for a separator 5 (e.g., similar to theconfiguration shown in FIG. 1B). In some embodiments, instead of castingthe matrix directly onto the electrode, it may be cast separately, andapplied in one or more portions, e.g., as a sheet cut to fit between theelectrodes.

At each electrode 3, the space between adjacent pCNTs is filled bypolymer electrolyte 6. When a voltage is applied to the device terminals8, ions in the electrolyte and charge of opposite sign in the electrode3 accumulate at the interface between the pCNTs and the polymerelectrolyte 6 (e.g., as shown in FIG. 1B). The energy stored in theelectric field at this double-layer of charge scales with the appliedvoltage, electrode surface area, capacitance, and amount of polymerelectrolyte stored in each porous electrode. The peak power of theultracapacitor scales with the applied voltage and theelectrode-electrolyte conductivity.

The electrolyte ions access the pCNT electrodes 3 during charge anddischarge by traveling through the hosting polymer matrix. In someembodiments, additives may be included in the polymer to promotedenhanced ion mobility. For example, in some embodiments, inorganic highsurface area additives such may be used that create defects in thepolymer matrix and promote enhanced ion mobility thus increasing theconductivity of the solid state electrolyte. An electron micrograph ofan example of a nanoporous ionic fluid doped polymer matrix is shown inFIG. 10.

Exemplary additives include fumed oxides such as fumed silicon oxide orfumed aluminum oxide, barium titanate, barium strontium titanium oxide,and the like. Other suitable additives include other inorganic orceramic powders (e.g., alumina, titania, magnesia, aluminosilicates, ortitanates such as BaTiO₃) or clays (e.g., bentonite or montmorilloniteand their derivatives).

In some embodiments, the additives may have a small average particle,e.g., of less than 100 nm, 50 nm, 40 nm, 30 nm, 10 nm, 5 nm, 2 nm, orless, e.g., in the range of 1 nm-100 nm or any sub-range thereof. Invarious embodiments, the concentration of additives in the ionic liquiddope polymer electrolyte material may be, e.g., in the range of 1%-50%by weight, or any sub-range thereof.

In some embodiments, the energy storage material may be a layer ofhighly purified carbon nanotubes or “pCNT”. In some embodiments, theCNTs may be produced with a Chemical Vapor Deposition process, e.g., ofthe type described herein. The CNTs may be purified, e.g., through anannealing process to form pCNTs. Unlike activated carbon, activatedcarbon fibers and activated aerogel, pCNTs do not present intrinsicimpurities and oxygen functional groups instilled by the activationprocess, thus allowing for lower leakage current at high temperatures.

In some embodiments the pCNTs may be substantially free of contaminatesincluding binders, adhesives, and the like. pCNT electrodes do notrequire binder or adhesives to have mechanical stability, thanks to thelarge Van de Waals forces (gecko effect) between pCNTs, that keep eachfilament attached and parallel to each other (as shown in FIG. 11).

In some embodiments, pCNT assemblies can be transferred onto porousmetallic current collectors without using adhesives. In someembodiments, the inert nature of our pCNT based electrode, due to theabsence of activation processes, binders, adhesives and oxygen groupsleads to a higher operating temperature. The purity of the pCNTelectrode may facilitate high temperature operation: oxygen groups andother contaminants coming from the synthesis process, will have to beremoved from the CNT structure to reduce spurious faradaic reaction athigh temperature.

In some embodiments, a pCNT based electrode with total average thicknessof 50 μm or less (e.g., in the range of 1 μm to 50 μm or any sub-rangethereof) may be used in order to allow the penetration of the polymerelectrolyte into each pore of the electrode (i.e., the void spacesbetween pCNTs). The channel-like morphology of the active material willfacilitate the access of the ions contained in the ionic liquid.

In some embodiments, the average pore diameter of the electrode isselected to be larger than the average diameter of the ions contained inpolymer electrolyte, which typically have average diameter of 0.5-2 nm.This may increase accessibility of the ions to the electrode. In someembodiments, the average pore diameter will be greater than about 2 nm,5 nm, 10 nm, 15 nm or more, e.g., in the range of 2 nm to 50 nm or anysub-range thereof. In some embodiments, the average pore size can becontrolled through the CNT synthesis and subsequent electrodefabrication. Pressure, temperature and feedstock gas flow during the CVDsynthesis may be adjusted in other to control the CNT spacing anddiameter, while the pressure during roll-to-roll transfer may beadjusted to control the total thickness and density of the pCNT activematerial.

In some embodiments, the pCNT may include less than 200 ppm, 100 ppm, 50ppm, 10 ppm. 5 ppm, 4 ppm, 3 ppm, 2 ppm, 1 ppm or less (by weight orvolume) of impurities including, e.g., halides, moisture, and oxygenfunctional groups.

In some embodiments, CNTs are grown using a CVD process on a hightemperature metallic substrate. Examples of substrate materials areTungsten or Ni—Fe—Co alloys. After synthesis CNTs may be purifiedthrough a low pressure annealing process. The oxygen groups (OH, COOH)that are attached to the outer wall of the CNTs after synthesis mayberemoved during a low pressure high temperature (e.g., T>800° C.)treatment in inert gas (e.g., Argon, Helium, Nitrogen, or combinationsthereof).

During this step the oxygen groups will be outgassed, and the so formedpCNTs will show a graphitized more electrochemically stable structurefor high temperature operations. Physical and structuralcharacterization tests (such as Raman Spectroscopy, TGA) may beperformed to corroborate the removal of the oxygen groups.

In some embodiments, the electrode 6 may be fabricated as follows. Theactive material is composed of the pCNTs. These structures areintrinsically extremely conductive and impurity free. The electrodecurrent collector 2 may be very conductive and electrochemically stable.A suitable current collector 2 is an etched metallic foil such as etchedaluminum foil. In some embodiments, pCNTs are transferred from the hightemperature metallic substrate to the etched aluminum current collector,e.g., via a roll-to-roll step. The Van der Waals forces between pCNTsand the aluminum foil will create a good mechanical and electricalcontact, thus forming a high surface area and low resistancebinder-free, adhesive-free electrode. Pressure and speed are theparameters to be controlled during this step since they affect thedensity and total thickness of the final electrode.

Returning to the electrolyte 6, in some embodiments, one or moreselected ionic liquids will be inserted in the hosting polymer matrix bydissolving the polymer in polar solvents and subsequently adding aselected amount of ionic liquid in the mixture. This mixture may becasted, e.g., on top of the pCNT electrodes, to form separate membranes.The solvent contained in the mixture can be removed, e.g., byevaporation in vacuum. The deposited ionic liquid polymer compound willform a flexible membrane. Thus, the polymer electrolyte may be formed inthe pCNT electrode pores and as a separate self-standing membrane thatmay be used to securely separate the electrodes in order to preventshort circuits once the ultracapacitor is assembled.

In some embodiments, the polymer electrolyte may be fabricated in anenvironment configured to prevent impurities, e.g., a dry environmentunder inert gas. In some embodiments, the polymer electrolyte mayinclude less than 200 ppm, 100 ppm, 50 ppm, 10 ppm, 5 ppm, 4 ppm, 3 ppm,2 ppm, 1 ppm or less (by weight or volume) of impurities including,e.g., halides, moisture.

In various embodiments, the polymer material may be chosen for highmechanical and chemical stability at temperatures above the maximumoperating temperature of the ultracapacitor. For example, in someembodiments the polymer remains substantially solid (e.g., sufficientlysolid to mechanically separate the electrodes of the ultracapacitor) attemperatures up to at least 300 C, 325 C, 350 C, 375 C, 400 C, 425 C,450 C, 475 C, 500 C or more. In some embodiments the polymer has adecomposition temperature of at least 300 C, 325 C, 350 C, 375 C, 400 C,425 C, 450 C, 475 C, 500 C or more. In various embodiments, the polymermay include Polyimide (PI), Polybenzimidazole (PBI),Polyetheretherketone (PEEK), Polytetrafluoroethylene (PTFE),Poly(vinylidenefluoride-hexafluoropropylene) (PVDF-HFP), Polysulfone(PSU), Polyethersulfone (PES). Or the like, and combinations thereof.

In some embodiments, the ionic liquid may be selected for a highdecomposition temperature, e.g., greater than 300 C, 325 C, 350 C, 375C, 400 C, 425 C, 450 C, 475 C, 500 C, or more. Exemplary ionic liquidsinclude: 1-Butyl-2,3-dimethylimidazoliumbis(trifluoromethylsulfonyl)imide, l-Ethyl-3-methylimidazoliumbis(pentafluoroethylsulfonyl)imide, 1-Ethyl-2,3-dimethylimidazoliumhexafluorophosphate, 1-Butyl-3-methylpyrrolidiniumbis(trifluoromethylsulfonyl)imide, 1-Butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide, 1-Butyl-3-methylimidazoliumtrifluoromethanesulfonate, and combinations thereof.

In various embodiments, the concentration of ionic liquid in the polymermaterial may be, e.g., in the range of 1%-50% by weight, or anysub-range thereof.

In some embodiments, the ionic liquid doped polymer electrolyte may havea decomposition temperature of greater than 300 C, 310 C, 320 C, 330 C,340 C, 350 C, 360 C, 370 C, 380 C, 390 C, 400 C, or more. In someembodiments, the ionic liquid doped polymer electrolyte may be formed asa relatively thin membrane, e.g., with a thickness of less than about100μπι or less. In some embodiments, the ionic liquid doped polymerelectrolyte may have a conductivity at 300 C of greater than about 10mS/cm.

Exemplary Applications

In various embodiments, ultracapacitors of the type described herein maybe incorporated in a power system, e.g., of the types described inInternational Patent Application No. PCT/US14/29992 filed Mar. 15, 2014.For example, in various embodiments, the power system may include one ormore of an ultracapacitor charging circuit, an ultracapacitor monitoringcircuit, a cross over circuit, and a signal interface device such as amodular signal interface device, examples of all of which are describedin the reference incorporated herein. In various embodiments, theultracapacitor may be charged by another energy source, such as abattery, a generator, a wire line, etc.

In various embodiments, multiple ultracapacitors of the type describedherein may be incorporated in a power system for use over a wide rangeof temperatures. For example, the system may include a first set of oneor more ultracapacitors adapted for operation at low temperatures, butcapable of surviving higher temperatures when not in use. The system mayfurther include a second set of one or more ultracapacitors adapted foroperation at high temperatures, but capable of surviving lowertemperatures when not in use. The system may include a temperaturesensor (or an ultracapacitor performance sensor) and control electronicscapable of switching between the two sets of ultracapacitors to use theappropriate set for the ambient conditions (as determined directly froma temperature sensor, or indirectly based on system performance). Invarious embodiments, more than two sets of capacitors may be used, e.g.,with each set adapted to operate in a respective temperature range. Insome embodiments, such systems may be configured to have operatingtemperature ranges of e.g., −55 C C to 300 C or any sub-range thereof.In an embodiment, the ultracapacitor that utilizes the electrolyte isconfigured to output electrical energy at operating voltages throughoutan operating voltage range, the operating voltage range being betweenabout 0 V and about 0.5 V.

Ultracapacitors described herein may be used in a variety ofapplications. In general, such ultracapacitors may be employed in powersystems used in extreme conditions (e.g., low and/or high temperatures,high mechanical shock and vibration, etc.), e.g., to provide high poweroutput. In various embodiments, the ultracapacitors may be charged froma relatively low rated source (e.g., low voltage, low current, lowpower, low reliability, and combinations thereof) and provide, e.g.,pulses of power (e.g., at higher voltage, higher current, higher power,and combinations thereof) or “smoothed” output with greater reliabilitythan the charging source. For example, in some embodiments, therelatively low rated source may include a battery, a solar cell, athermoelectric generator, a mechanical generator, or any other suitablesource.

In various embodiments, power systems including ultracapacitorsdescribed herein may be used to provide power to one or more componentswith high power demand. For example, in the aerospace context (e.g.,airplanes, helicopters, drones, missiles, rockets, space launchvehicles, space exploration vehicles, and the like), the ultracapacitorsmay be charged over time by a relatively low power source (e.g., themain electrical system of an aerospace vehicle) and then discharged toprovide relatively short pulses of high power output, e.g., to power oneor more actuators (e.g., to actuate a control surface, door, landinggear, or other component of the vehicle), a sensor (e.g., a locationsensor such as a GPS sensor, a radar sensor, an infrared sensor such asforward or downward looking infrared sensors, an acoustic sensor, apressure sensor, etc.), a communication device (e.g., a radio or opticalcommunication link, a satellite communication link, etc.), or any othersuitable component.

In various embodiments, the teachings herein enable performance ofultracapacitors in extreme conditions. Ultracapacitors fabricatedaccordingly may, for example, operate at temperatures above 300 C for10,000 charge/discharge cycles and/or over 100 hours or more at avoltage of 0.5V or more while exhibiting and increase in ESR or lessthan 100%, e.g. less than about 85% and a decrease in capacitance ofless than about 10%. In some embodiments, such ultracapacitors may havea volumetric capacitance of about 5 Farad per liter (F/L), 6 F/L, 7 F/L,8 F/L, 8 F/L, 10 F/L or more, e.g., in the range of about 1 to about 10F/L or any sub-range thereof.

In some embodiments, ultracapacitors of the types described herein mayexhibit any of: a high volumetric energy density (e.g., exceeding 0.25Wh/L, 0.5 Wh/L, 1 Wh/L, 2 Wh/L, 3 Wh/L, 4 Wh/L, 5 Wh/L, 6 Wh/L, 7 Wh/L,8 Wh/L, 9 Wh/L, 10 Wh/L, 11 Wh/L, 12 Wh/L, 15 Wh/L, 18 Wh/L, 20 Wh/L, ormore), a high gravimetric energy density (e.g., exceeding 5 Wh/kg, 6Wh/kg, 7 Wh/kg, 8 Wh/kg, 9 Wh/kg, 10 Wh/kg, 11 Wh/kg, 12 Wh/kg, 15Wh/kg, 18 Wh/kg, or more), a high volumetric power density (e.g.,exceeding 30 kW/L, 40 kW/L, 50 kW/L, 60 kW/L, 70 kW/L, 80 kW/L, 90 kW/L,100 kW/L, 110 kW/L, 120 kW/L, or more), a high gravimetric power density(e.g., exceeding 30 kW/kg, 40 kW/kg, 50 kW/kg, 60 kW/kg, 70 kW/kg, 80kW/kg, 90 kW/kg, 100 kW/kg, 110 kW/kg, 120 kw/KG or more), andcombinations thereof. In some embodiments, ultracapacitors of the typesdescribed herein demonstrate high performance as indicated by theproduct of energy density and power density, e.g., exceeding 300Wh-kW/L{circumflex over ( )}2, 500 Wh-kW/L{circumflex over ( )}2, 700Wh-kW/L{circumflex over ( )}2, or more.

In some embodiments, ultracapacitors of the type described herein may behighly resistant to shock and vibration. For example, in someembodiments, the ultracapacitor may operate for hundred, thousands, tensof thousands or more charge/discharge cycles even in the presence ofshocks of up to 1000 G or more and vibrations of up to 60 Grms or more.

It should be recognized that the teachings herein are merelyillustrative and are not limiting of the invention. Further, one skilledin the art will recognize that additional components, configurations,arrangements and the like may be realized while remaining within thescope of this invention. For example, configurations of layers,electrodes, leads, terminals, contacts, feed-throughs, caps and the likemay be varied from embodiments disclosed herein. Generally, designand/or application of components of the ultracapacitor andultracapacitors making use of the electrodes are limited only by theneeds of a system designer, manufacturer, operator and/or user anddemands presented in any particular situation.

Exemplary Wide Temperature Ultracapacitor

Disclosed herein is an energy storage device, e.g., comprising an EDLCthat provides users with improved performance in a wide range oftemperatures. For example, the energy storage device may be operable attemperatures ranging from about as low as −40 C (degrees Celsius) oreven below, to as high as about 250 C. In some embodiments, the energystorage device is operable temperatures as high as about 200 C, as highas about 210 C, as high as about 220 C, as high as about C, as high asabout 240 degrees C., or as high as about 250 C. In some embodiments,the ultracapacitorcapacitor is operable temperatures as low as about 0degrees Celsius, as low as about 0 C, −10 C, −20 C, −30 C, −40 C, −50 C,−60 C, −70. C, −80 C, −90 C, −100 C, −110 C, or even less.

In general, the device includes energy storage media that is adapted forproviding high power density and high energy density when compared toprior art devices. The device includes components that are configuredfor ensuring operation over the temperature range, and includes any oneor more of a variety of forms of electrolyte that are likewise rated forthe temperature range. The combination of construction, energy storagemedia and electrolyte result in capabilities to provide robust operationunder extreme conditions. To provide some perspective, aspects of anexemplary embodiment are now introduced.

As shown in FIGS. 1A and 1B, exemplary embodiments of a capacitor areshown. In each case, the capacitor is an “ultracapacitor 10.” Thedifference between FIG. 1A and FIG. 1B is the inclusion of a separatorin exemplary ultracapacitor 10 of FIG. 1A. The concepts disclosed hereingenerally apply equally to any exemplary ultracapacitor 10. Certainelectrolytes of certain embodiments are uniquely suited to constructingan exemplary ultracapacitor 10 without a separator. Unless otherwisenoted, the discussion herein applies equally to any ultracapacitor 10,with or without a separator.

The exemplary ultracapacitor 10 is an electric double-layer capacitor(EDLC). The EDLC includes at least one pair of electrodes 3 (where theelectrodes 3 may be referred to as a negative electrode 3 and a positiveelectrode 3, merely for purposes of referencing herein). When assembledinto the ultracapacitor 10, each of the electrodes 3 presents a doublelayer of charge at an electrolyte interface. In some embodiments, aplurality of electrodes 3 is included (for example, in some embodiments,at least two pairs of electrodes 3 are included). However, for purposesof discussion, only one pair of electrodes 3 are shown. As a matter ofconvention herein, at least one of the electrodes 3 uses a carbon-basedenergy storage media 1 (as discussed further herein) to provide energystorage. However, for purposes of discussion herein, it is generallyassumed that each of the electrodes includes the carbon-based energystorage media 1. It should be noted that an electrolytic capacitordiffers from an ultracapacitor because, among other things, metallicelectrodes differ greatly (at least an order of magnitude) in surfacearea.

Each of the electrodes 3 includes a respective current collector 2 (alsoreferred to as a “charge collector”). In some embodiments, theelectrodes 3 are separated by a separator 5. In general, the separator 5is a thin structural material (usually a sheet) used to separate thenegative electrode 3 from the positive electrode 3. The separator 5 mayalso serve to separate pairs of the electrodes 3. Once assembled, theelectrodes 3 and the separator 5 provide a storage cell 12. Note that,in some embodiments, the carbon-based energy storage media 1 may not beincluded on one or both of the electrodes 3. That is, in someembodiments, a respective electrode 3 might consist of only the currentcollector 2. The material used to provide the current collector 2 couldbe roughened, anodized or the like to increase a surface area thereof.In these embodiments, the current collector 2 alone may serve as theelectrode 3. With this in mind, however, as used herein, the term“electrode 3” generally refers to a combination of the energy storagemedia 1 and the current collector 2 (but this is not limiting, for atleast the foregoing reason).

At least one form of electrolyte 6 is included in the ultracapacitor 10.The electrolyte 6 fills void spaces in and between the electrodes 3 andthe separator 5. In general, the electrolyte 6 is a substance thatdisassociates into electrically charged ions. A solvent that dissolvesthe substance may be included in some embodiments of the electrolyte 6,as appropriate. The electrolyte 6 conducts electricity by ionictransport.

Generally, the storage cell 12 is formed into one of a wound form orprismatic form which is then packaged into a cylindrical or prismatichousing 7. Once the electrolyte 6 has been included, the housing 7 maybe hermetically sealed. In various examples, the package is hermeticallysealed by techniques making use of laser, ultrasonic, and/or weldingtechnologies. In addition to providing robust physical protection of thestorage cell 12, the housing 7 is configured with external contacts toprovide electrical communication with respective terminals 8 within thehousing 7. Each of the terminals 8, in turn, provides electrical accessto energy stored in the energy storage media 1, generally throughelectrical leads which are coupled to the energy storage media 1.

In the exemplary ultracapacitor 10, the energy storage media 1 is formedof carbon nanotubes. The energy storage media 1 may include othercarbonaceous materials including, for example, activated carbon, carbonfibers, rayon, graphene, aerogel, carbon cloth, and a plurality of formsof carbon nanotubes. Activated carbon electrodes can be manufactured,for example, by producing a carbon base material by carrying out a firstactivation treatment to a carbon material obtained by carbonization of acarbon compound, producing a formed body by adding a binder to thecarbon base material, carbonizing the formed body, and finally producingan active carbon electrode by carrying out a second activation treatmentto the carbonized formed body. Carbon fiber electrodes can be produced,for example, by using paper or cloth pre-form with high surface areacarbon fibers.

In some embodiments, the electrode of the ultracapacitor 10 includes acurrent collector comprising aluminum with an aluminum carbide layer onat least one surface, on which at least one layer of carbon nanotubes(CNTs) is disposed. The electrode may comprise vertically-aligned,horizontally-aligned, or nonaligned (e.g., tangled or clustered) CNTs.The electrode may comprise compressed CNTs. The electrode may comprisesingle-walled, double-walled, or multiwalled CNTs. The electrode maycomprise multiple layers of CNTs. In some embodiments, the carbide layerincludes elongated whisker structures with a nanoscale width. In someembodiments, the whiskers protrude into the layer of CNTs. In someembodiments, the whiskers protrude through an intervening layer (e.g.,an oxide layer) into the layer of CNTs. Further details relating toelectrodes of this type may be found in U.S. Provisional PatentApplication No. 62/061,947 “ELECTRODE FOR ENERGY STORAGE DEVICE USINGANODIZED ALUMINUM” filed Oct. 9, 2014, the entire contents of which areincorporated herein by reference.

In some embodiments, material used to form the energy storage media 1may include material other than pure carbon (and the various forms ofcarbon as may presently exist or be later devised). That is, variousformulations of other materials may be included in the energy storagemedia 1. More specifically, and as a non-limiting example, at least onebinder material may be used in the energy storage media 1, however, thisis not to suggest or require addition of other materials (such as thebinder material). In general, however, the energy storage media 1 issubstantially formed of carbon, and may therefore referred to herein asa “carbonaceous material,” as a “carbonaceous layer” and by othersimilar terms. In short, although formed predominantly of carbon, theenergy storage media 1 may include any form of carbon (as well as anyadditives or impurities as deemed appropriate or acceptable) to providefor desired functionality as energy storage media 1.

In one set of embodiments, the carbonaceous material includes at leastabout 60% elemental carbon by mass, and in other embodiments at leastabout 75%, 85%, 90%, 95% or 98%) by mass elemental carbon.

Carbonaceous material can include carbon in a variety forms, includingcarbon black, graphite, and others. The carbonaceous material caninclude carbon particles, including nanoparticles, such as nanotubes,nanorods, graphene sheets in sheet form, and/or formed into cones, rods,spheres (buckyballs) and the like.

Some embodiments of various forms of carbonaceous material suited foruse in energy storage media 1 are provided herein as examples. Theseembodiments provide robust energy storage and are well suited for use inthe electrode 3. It should be noted that these examples are illustrativeand are not limiting of embodiments of carbonaceous material suited foruse in energy storage media 1.

In general, the term “electrode” refers to an electrical conductor thatis used to make contact to another material which is often non-metallic,in a device that may be incorporated into an electrical circuit.Generally, the term “electrode,” as used herein, is with reference tothe current collector 2 and the additional components as may accompanythe current collector 2 (such as the energy storage media 1) to providefor desired functionality (for example, the energy storage media 1 whichis mated to the current collector 2 to provide for energy storage andenergy transmission). An exemplary process for complimenting the energystorage media 1 with the current collector 2 to provide the electrode 3is now provided.

The separator 5 may be fabricated from various materials. In someembodiments, the separator 5 is non-woven glass. The separator 5 mayalso be fabricated from fiberglass, ceramics and flouro-polymers, suchas polytetrafluoroethylene (PTFE), commonly marketed as TEFLON™ byDuPont Chemicals of Wilmington, Del. For example, using non-woven glass,the separator 5 can include main fibers and binder fibers each having afiber diameter smaller than that of each of the main fibers and allowingthe main fibers to be bonded together.

For longevity of the ultracapacitor 10 and to assure performance at hightemperature, the separator 5 should have a reduced amount of impuritiesand in particular, a very limited amount of moisture contained therein.In particular, it has been found that a limitation of about 200 ppm ofmoisture is desired to reduce chemical reactions and improve thelifetime of the ultracapacitor 10, and to provide for good performancein high temperature applications. Some embodiments of materials for usein the separator 5 include polyamide, polytetrafluoroethylene (PTFE),polyether-ether-ketone (PEEK), aluminum oxide (Al₂O₃), fiberglass,glass-reinforced plastic (GRP), polyester, nylon, and polyphenylenesulfide (PPS).

In general, materials used for the separator 5 are chosen according tomoisture content, porosity, melting point, impurity content, resultingelectrical performance, thickness, cost, availability and the like. Insome embodiments, the separator 5 is formed of hydrophobic materials.

Note that, in some embodiments, the ultracapacitor 10 does not requireor include the separator 5. For example, in some embodiments, such aswhere the electrodes 3 are assured of physical separation by a geometryof construction, it suffices to have electrolyte 6 alone between theelectrodes 3. More specifically, and as an example of physicalseparation, one such ultracapacitor 10 may include electrodes 3 that aredisposed within a housing such that separation is assured on acontinuous basis. A bench-top example would include an ultracapacitor 10provided in a beaker.

The ultracapacitor 10 may be embodied in several different form factors(i.e., exhibit a certain appearance). Examples of potentially usefulform factors include, a cylindrical cell, an annular or ring-shapedcell, a flat prismatic cell or a stack of flat prismatic cellscomprising a box-like cell, and a flat prismatic cell that is shaped toaccommodate a particular geometry such as a curved space. A cylindricalform factor may be most useful in conjunction with a cylindrical tool ora tool mounted in a cylindrical form factor. An annular or ring-shapedform factor may be most useful in conjunction with a tool that isring-shaped or mounted in a ring-shaped form factor. A flat prismaticcell shaped to accommodate a particular geometry may be useful to makeefficient use of “dead space” (i.e., space in a tool or equipment thatis otherwise unoccupied, and may be generally inaccessible).

The electrolyte 6 includes a pairing of cations 9 and anions 11 and mayinclude a solvent or other additives. The electrolyte 6 may be referredto as a “ionic liquid” as appropriate. Various combinations of cations9, anions 11 and solvent may be used.

In some embodiments, the electrolyte 6 may be adapted such that theultracapacitor 10 has an operational temperature range that extends tolow temperatures, e.g., less than about −40 C, −50 C, −60 C, −70 C, −80C, −90 C, −100 C, −110 C, −120 C, −130 C, −140 C, −150 C, −160 C, −170C, −180 C, −190 C, −200 C, or less. In some embodiments, the operationaltemperature range may also extend to relatively high temperatures, e.g.,greater than about 0 C, 10 C, 20 C, 30 C, 40 C, 50 C, 60 C, 70 C, 80 C,90 C, 100 C, 110 C, 120 C, 130 C, 140 C, 150 C, 160 C, 170 C, 180 C, 190C, 200 C, 210 C, 220 C, 230 C, 240 C, 250 C, or more. For example, invarious embodiments, the operational temperature range may be, e.g.,−200 C to 250 C, or any subrange thereof, e.g., −60 C to 70 C, −70 C to70 C, −80 C to 70 C, −90 C to 70 C, −100 C to 70 C, −110 C to 70 C, −120C to 70 C, −130 C to 70 C, −60 C to 75 C, −70 C to 75 C, −80 C to 75 C,−90 C to 75 C, −100 C to 75 C, −110 C to 75 C, −120 C to 75 C, −130 C to75 C, −60 C to 80 C, −70 C to 80 C, −80 C to 80 C, −90 C to 80 C, −100 Cto 80 C, −110 C to 80 C, −120 C to 80 C, or −130 C to 80 C.

In some embodiments, such performance may be provided at least in partby use of solvent combined with the cations 9 and anions 11 (cations 9and anions 11 are referred to collectively as a “salt” or “ionicliquid”) to form the electrolyte 6. The solvent may be chosen to have alow melting point (e.g., significantly lower than the low end of theoperating temperature range of the ultracapacitor 10) and a highdielectric constant to improve solubility of the salt and achieve highionic conductivity (which tends to be reduced at lower temperatures).

However, in many cases, solvents with low melting point have relativelylow dielectric constant, and vice versa. Accordingly, in someembodiments a combination of at least two solvents are used. The firstsolvent may be selected to provide relatively high dielectric constant.For example, in some embodiments, the first solvent may have adielectric constant at 25 C greater than about 2, e.g., preferablegreater than about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, or more, e.g.,in the range of 2 to 50, or any subrange thereof, such as about 20 toabout 40. In some embodiments, the first solvent may be selected toexhibit relatively low viscosity. For example, in some embodiments, thefirst solvent may exhibit a viscosity of (in units of centiPoise or 0.01Poise) of less than about 2, 1.5, 1.0, 0.5, 0.4, 0.3, 0.2 or less.

In some embodiments, the first solvent may have a relatively highmelting point, e.g., greater than about −80 C, −70 C, −60 C, −50 C, −40C, or more, e.g., greater than the lower limit of the operatingtemperature range of the ultracapacitor 10. In some such embodiments,the second solvent (discussed in greater detail below) may be selectedto have a melting point lower than the first solvent, such that theoverall melting point of the electrolyte 6 is reduced, e.g., such thatit is less than the lower limit of the operating temperature range ofthe ultracapacitor 10.

Examples of materials suitable for use as the first solvent include, butare not limited to: acetonitrile, trimethylamine, propylene carbonate,gamma-butylrolactone, and the like. In some embodiments, the firstsolvent and or the second solvent may be selected from acetonitrile,propylene carbonate, methyl formate, ethyl acetate, methyl acetate,propionitrile, butyronitrile, and 1,3-dioxolane.

In some embodiments, the second solvent may have a lower dielectricconstant than the first solvent, but may exhibit some other desirableproperty. For example, in some embodiments, the second solvent may beselected to have a melting point lower than the first solvent, such thatthe overall melting point of the electrolyte 6 is reduced. For example,the second solvent may have a melting point that is less than theboiling point of the first solvent by at least 10 C, 20 C, 30 C, 40 C,50 C, 60 C, 70 C, 80 C, 90 C, 100 C, or more.

In some embodiments, the second solvent may also exhibit relatively lowviscosity. In some embodiments, the first solvent may exhibit aviscosity of (in units of centiPoise or 0.01 Poise) of less than about2, 1.5, 1.0, 0.5, 0.4, 0.3, 0.2 or less.

Examples of materials suitable for use as the second solvent include,but are not limited to the solvents provided in FIG. 12. In variousembodiments, an ester solvent may be used as the second solvent. In someembodiments of the invention, (e.g., where the first solvent includesacetonitrile) the second solvent may include an organic carbonate,ether, formate, ester or substituted nitrile.

In various embodiments, the ratio of the amount (by mass or volume) ofthe first solvent to the second solvent may be any suitable value. Forexample, in some embodiment the ratio may be in the range of, e.g., 1:1to 10:1, or any subrange thereof, e.g., about 1:1, about 2:1, about 3:1,or about 4:1.

In some embodiments, more or less than two solvents may be used. Ingeneral, multiple solvents may be combined to provide suitabletrade-offs in performance in any of several aspects including: meltingpoint, boiling point, disintegration temperature, salt solubility,ultracapacitor capacitance, ultracapacitor equivalent series resistance,and the like.

In some embodiments, the molarity of the salt in the electrolyte 6 maybe selected to enhance the performance of the ultracapacitor 10. In someembodiments, at low temperatures, choosing a reduced concentration ofsalt unexpectedly provides for increased low temperature ultracapacitorperformance (e.g., increased capacitance or decreased equivalent seriesresistance at low temperature). Not wishing to be bound be theory, it isbelieved that lower concentration reduces or eliminates precipitation ofthe salt into pores in the energy storage media 1, thereby reducing thesurface area of the media.

In some embodiments, the molarity of the salt may be selected asfollows. First, some or all of the other relevant design parameters ofthe ultracapacitor 10 (e.g., electrolyte type, energy storage mediatype, separator material, form factor, etc.) may be set. Next, themolarity of the salt in the electrolyte 6 is varied (e.g., by preparingseveral otherwise identical test cells with varying salt molarity).Next, at least one performance metric (e.g., capacitance, ESR, and/orvoltage window) of the ultracapacitor is measured, e.g., at a desiredminimum operating temperature as a function of salt molarity (e.g., overthe range of 0.1 M to 10 M, or a selected subrange thereof). Finally adesired molarity is selected based on the measured performance metric(e.g., by interpolating a molarity corresponding to an optimumperformance metric).

In some embodiments, the molarity of the salt in the electrolyte 6 maybe in the range of, e.g., 0.1 M to 10 M, or a selected subrange thereof,such as 0.25 M to 2.5 M.

In various embodiments, the salt may include any of the cations andanions set forth in FIG. 13. In some embodiments, it may be advantageousto select a salt featuring a highly asymmetric cation, which may promotea lower melting point of the resulting ionic liquid.

In some embodiments, the salt may include more than one ionic liquid(i.e., more than one cation, anion, or both). In some such embodiments,the cations of each of the ionic liquids may be selected to havesignificantly different structures, which may promote a lower meltingpoint of the resulting ionic liquid combination. For example, in someembodiments, the first cation may include one or more functional groupsnot present in the second cation. In some embodiments, the first cationmay be more highly branched than the second cation, etc.

Examples of suitable salts for use in electrolyte 6 include, but are notlimited to quaternary ammonium salts such as tetraethylammoniumtetrafluoroborate, triethylmethylammonium tetrafluoroborate, spiro-typequaternary ammonium salts such as spiro-(1,1′)-bipyrrolidiniumtetrafluoroborate, and alkyl quaternary ammonium salts suchtetraalkylammonium salts. In some embodiments, other suitable cations,anions, and combinations thereof for use as ionic liquids in electrolyte6 include those set forth in the FIG. 13.

In some embodiments, the electrolyte 6 may include a combination of aliquid gas (i.e., a liquefied material that would be a gas at, e.g., atemperature of 0 C and a pressure of 760 mmHg), and one or more salts(e.g., of any of the types disclosed herein). For example, the housing 7of the ultracapacitor 10 may include a pressure vessel used to containthe liquid gas a sufficient pressure to maintain the material in theliquid state over the operational temperature range of theultracapacitor 10. For example, the pressure vessel may include ametallic (e.g., steel) material, a composite material (e.g., woundcarbon fiber), or combinations thereof. In some embodiments, all or aportion of the interior surface of the vessel may be coated with amaterial that is less chemically reactive with the electrolyte 6 thanthe underlying material of the vessel. In some embodiments, the vesselis compliant with one or more pressure vessel safety standards known inthe art, including, e.g., one or more of ASME Boiler and Pressure VesselCode Section VIII: Rules for Construction of Pressure Vessels, AIAAS-080-1998: AIAA Standard for Space Systems—Metallic Pressure Vessels,Pressurized Structures, and Pressure Components, AIAA S-081A-2006: AIAAStandard for Space Systems—Composite Overwrapped Pressure Vessels(COPVs).

In some embodiments, the vessel may include one or more thermalinsulating elements. For example, in some embodiments, the vessel may beconstructed as a vacuum flask or Dewar flask of the type familiar fromcryogenic storage applications.

Examples of liquid gases suitable for use in some embodiments includes,but is not limited to, liquid nitrogen, liquid argon, liquid helium, andliquid chlorofluorocarbons (e.g., hydrochlorofluorocarbons such aschlorodifluoromethane).

In various embodiments, the liquid gas may be produced and transferredto the housing 7 using any suitable technique known in the art, such ascryogenic distillation, e.g., of liquefied air.

In certain embodiments, electrolyte 6 may include one or more additionaladditives, e.g., gelling agents (e.g., silica or silicates), otherinorganic or ceramic powders (e.g., alumina, titania, magnesia,aluminosilicates, or titanates such as BaTiO₃), clays (e.g., bentoniteor montmorillonite and their derivatives), solvents, polymeric materials(including polymeric microbeads), plasticizers, and combinationsthereof. In an embodiment, the additive comprises a gelling agent thatcontains a mesoporous inorganic oxide, a polycrystalline inorganic oxideor a microcrystalline inorganic oxide. Porous inorganic oxides areuseful additives for providing a gel electrolyte. Exemplary additivesinclude silica, silicates, alumina, titania, magnesia, aluminosilicates,zeolites, or titanates.

For example, an electrolyte according to one embodiment of the presentinvention comprises an ionic liquid, e.g., one of the ionic liquidsdescribed herein, such as an ionic liquid comprising a cation, asdescribed herein, and an anion, as described herein, and fumed silica asa gelling agent, which are mixed in a ratio to produce an ionic liquidgel. Certain embodiments may employ a different form of silica as agelling agent, e.g., silica gel, mesoporous silica, or amicrocrystalline or polycrystalline form of silica. The amount of theadditive will vary according to the nature of the application and istypically in the range of about 2 wt. % to about 20 wt. %, potentiallyas much as about 50 wt. %, of the electrolyte. In these embodiments,impurities may also be minimized in the ultracapacitor cell as describedabove, specifically less than 1,000 ppm moisture, less than 500 ppmmoisture, and preferably less than 200 ppm moisture. In addition, otherimpurities were minimized in these embodiments as described above,particularly halide impurities and organic impurities.

In certain embodiments, an ultracapacitor comprising a gel electrolyteis disclosed. Such ultracapacitors can also operate stably, e.g., athigh voltages.

A suitable concentration of additive will be determined based on thedesired properties of the electrolyte and/or ultracapacitor, e.g., theviscosity of the electrolyte or the leakage current, capacitance, or ESRof the ultracapacitor. The specific surface area (SSA) also affects theproperties of the electrolyte and the resultant ultracapacitor.Generally, a high SSA is desirable, e.g., above about 100 m²/g, aboveabout 200 m²/g, about 400 m²/g, about 800 m²/g, or about 1000 m²/g. Theviscosity of the electrolyte comprising the additive affects theperformance of the resultant ultracapacitor and must be controlled byadding an appropriate amount of the additive.

In certain embodiments, where an appropriate gel-based electrolyte isemployed, a separator-less ultracapacitor 10 can be prepared, as shownin FIG. 1B. A separator-less ultracapacitor 10 of FIG. 1B is prepared ina manner analogous a typical ultracapacitor having a separator, e.g., anultracapacitor of FIG. 1A, except that the gel-based electrolyte is of asufficient stability that a separator is not required.

In certain embodiments, a solid state polymeric electrolyte may beprepared and employed in an ultracapacitor. In such embodiments, apolymer containing an ionic liquid is cast by dissolving a polymer in asolvent together with an electrolyte and any other additives, e.g.,e.g., gelling agents (e.g., silica or silicates), other inorganic orceramic powders (e.g., alumina, titania, magnesia, aluminosilicates, ortitanates such as BaTiO₃), clays (e.g., bentonite or montmorillonite andtheir derivatives), solvents, other polymeric materials, plasticizers,and combinations thereof. After drying the cast polymer electrolyte filmcan be incorporated into an ultracapacitor using the techniques forassembling ultracapacitors described herein, except that the polymerelectrolyte replaces both the liquid (or gel) electrolyte and theseparator in the ultracapacitor. The polymer film may also be castdirectly onto the electrode of an ultracapacitor. Exemplary polymersinclude polyamide, polytetrafluoroethylene (PTFE), polyvinylidenefluoride-hexafluoropropylene copolymer (PVDF-HFP), polyether etherketone (PEEK), CRAFT, sulfonated poly(ether ether ketone) (SPEEK),crosslinked sulfonated poly(ether ether ketone) (XSPEEK), and otherpolymer and copolymers stable at high temperature and appropriate forhermetic applications.

The chart represented in FIGS. 14A and 14B shows experimentally obtainedperformance data for a number of ultracapacitor cells of the typedescribed herein. In each case, the ultracapacitor under test was anEDLC contained in a 7.9 cubic centimeter housing and featuring activatedcarbon energy storage material on each electrode. The electrolyte usedin EDLC included a salt of the type described herein in combined withacetonitrile solvent in the ratio set forth on the chart. The ESR andcapacitance for each cell was measured at a variety of temperatures. Theresults show remarkably stable performance at temperatures as low as −40C. The data below demonstrates that cells may have a capacitancevariance from room temperature to −40 C of less than 1%. Accordingly, itis expected that comparable performance will be evidences at even lowertemperatures, e.g., −50 C, −60 C, −70 C, −80 C, or lower, e.g., by useof techniques described above such as the use of multiple solvents,multiple salts, and/or pressurized liquid gas solvents.

Exemplary Applications

In various embodiments, ultracapacitors of the type described herein maybe incorporated in a power system, e.g., of the types described inInternational Patent Application No. PCT/US14/29992 filed Mar. 15, 2014.For example, in various embodiments, the power system may include one ormore of an ultracapacitor charging circuit, an ultracapacitor monitoringcircuit, a cross over circuit, and a signal interface device such as amodular signal interface device, examples of all of which are describedin the reference incorporated herein. In various embodiments, theultracapacitor may be charged by another energy source, such as abattery, a generator, a wire line, etc.

In some embodiments, the electronic components of the power system maybe adapted for extreme (e.g., low, high, or both) temperature use. Forexample, in some embodiments, the power system may incorporate lowtemperature electronics of the type described in Patterson, et al., LowTemperature Electronics for Space and Terrestrial Application (accessedJan. 11, 2015 athttps://www.google.com/webhp?sourceid=chrome-instant&ion=l&espv=2&ie=UTF-8#q=low%20temperature%20electronics). In some embodiments, the power system mayincorporate one or more heaters (e.g., thermoelectric heaters) toregulate the temperature of the electronics. However, in some otherembodiments, no active heating is used.

In various embodiments, multiple ultracapacitors of the type describedherein may be incorporated in a power system for use over a wide rangeof temperatures. For example, the system may include a first set ofultracapacitors adapted for operation at low temperatures, but capableof surviving higher temperatures when not in use. The system may furtherinclude a second set of ultracapacitors adapted for operation at hightemperatures, but capable of surviving lower temperatures when not inuse. The system may include a temperature sensor (or an ultracapacitorperformance sensor) and control electronics capable of switching betweenthe two sets of ultracapacitors to use the appropriate set for theambient conditions (as determined directly from a temperature sensor, orindirectly based on system performance). In various embodiments, morethan two sets of capacitors may be used, e.g., with each set adapted tooperate in a respective temperature range. In some embodiments, suchsystems may be configured to have operating temperature ranges of −200 Cto 250 C, or any subrange thereof such as −180 C to 250 C, −150 C to 250C, −125 C to 250 C, −100 C to 250 C, −80 C to 250 C, −70 C to 250 C, −60C to 250 C, or −50 C to 250 C.

Ultracapacitors described herein may be used in a variety ofapplications. In general, such ultracapacitors may be employed in powersystems used in extreme conditions (e.g., low and/or high temperatures,high mechanical shock and vibration, etc.), e.g., to provide high poweroutput. In various embodiments, the ultracapacitors may be charged froma relatively low rated source (e.g., low voltage, low current, lowpower, low reliability, and combinations thereof) and provide, e.g.,pulses of power (e.g., at higher voltage, higher current, higher power,and combinations thereof) or “smoothed” output with greater reliabilitythan the charging source. For example, in some embodiments, therelatively low rated source may include a battery, a solar cell, athermoelectric generator, a mechanical generator, or any other suitablesource.

In various embodiments, power systems including ultracapacitorsdescribed herein may be used to provide power to one or more componentswith high power demand. For example, in the aerospace context (e.g.,airplanes, helicopters, drones, missiles, rockets, space launchvehicles, space exploration vehicles, and the like), the ultracapacitorsmay be charged over time by a relatively low power source (e.g., themain electrical system of an aerospace vehicle) and then discharged toprovide relatively short pulses of high power output, e.g., to power oneor more actuators (e.g., to actuate a control surface, door, landinggear, or other component of the vehicle), a sensor (e.g., a locationsensor such as a GPS sensor, a radar sensor, an infrared sensor such asforward or downward looking infrared sensors, an acoustic sensor, apressure sensor, etc.), a communication device (e.g., a radio or opticalcommunication link, a satellite communication link, etc.), or any othersuitable component.

In some embodiments, power systems including ultracapacitors describedherein may be used as uninterrupted power sources or auxiliary powerunits, e.g., for use in aerospace vehicles.

In various embodiments, power systems including ultracapacitors of thetype described herein may be used in launch vehicles, e.g., to providepower for controlling pyrotechnic devices used to facilitate separationof launch vehicle stages. An exemplary system is shown in the FIG. 15.

In some embodiments, power systems including ultracapacitors of the typedescribed herein may be incorporated in extraterrestrial devices (e.g.,satellites, interplanetary probes, etc.). For example, in someembodiments, power systems including ultracapacitors described hereinmay be suitable for the use in as deep space systems such as explorationvehicles, communication transponders, radars, telescopes, and the like.

In various embodiments, power systems including ultracapacitors of thetype described herein may provide various advantages over prior powersystems. For example, in some embodiments, ultracapacitors may reduce oreliminate the need for high rated batteries that often are characterizedby low volumetric and gravimetric power density and/or may be prone tocatastrophic failure. In contrast, ultracapacitors of the type describedherein may have high volumetric and gravimetric power density. In someembodiments, ultracapacitors of the type described herein may be free orsubstantially free from materials associated with catastrophic failure.For example, in some embodiments, ultracapacitors of the type describedherein may be free or substantially free from highly flammable materialssuch as lithium or other alkali metals.

In some embodiments, power systems including low temperatureultracapacitors of the type described herein may reduce or eliminate theneed for heating elements (as the associated use of power for heating).For example, in some embodiments, power systems including lowtemperature ultracapacitors of the type described herein require noactive heating. For example, in some embodiments, power systemsincluding low temperature ultracapacitors of the type described hereinrequire no active heating for the ultracapacitor cells, e.g., onlyrequiring heating for associated electronics (e.g., ultracapacitorcontrol, management, monitoring, and other such electronics.)

As noted above, in some embodiments, power systems of the type describedherein may include both low temperature and high temperatureultracapacitors combined to provide a very wide operational temperaturerange. Such power systems may be suitable for use in, e.g., deep spaceexploration vehicles which may experience wide swings in operationaltemperature based on, e.g., the amount of sunlight incident on thevehicle.

Although the examples above focus on the use of low temperatureelectrolytes in ultracapacitors, it is to be understood that suchmaterials may be used in other applications. For example, in someembodiments low temperature ionic liquid materials of the type describedherein may be used, e.g., in electric propulsion devices (e.g., for usein propelling and/or maneuvering satellites or other space craft. Forexample, temperature ionic liquid materials of the type described hereinmay be used as propellant in propulsion devices of the type described inCourtney & Lozano, Ionic Liquid Ion Source Emitter Arrays Fabricated onBulk Porous Substrates for Spacecraft Propulsion, Thesis forMassachusetts Institute of Technology (2011) (accessed Jan. 10, 2015 athttp://ssl.mit.edu/publications/theses/PhD-2011-CourtneyDaniel.pdf).

In some embodiments, low temperature electrolytes of the type describedherein may be used in electrolytic capacitors (i.e., conventionalcapacitors that do not use an electric double layer to store energy).

In some embodiments, low temperature electrolytes of the type describedherein may be included in drilling fluid material, e.g., when drillingin low temperature regions such as polar regions.

In various embodiments, the teachings herein enable performance ofultracapacitors in extreme conditions. Ultracapacitors fabricatedaccordingly may, for example, operate at temperatures below −40 C (e.g.,−70 C, −80 C, −90 C, −100 C, −110 C or less) and as high as 150 C, 180C, 200 C, 210 C, 225 C, 250 C or more, e.g., for 10,000 charge/dischargecycles and/or over 100 hours or more at a voltage of 0.5V or more whileexhibiting and increase in ESR or less than 100%, e.g. less than about85% and a decrease in capacitance of less than about 10%. In someembodiments, such ultracapacitors may have a volumetric capacitance ofabout 5 Farad per liter (F/L), 6 F/L, 7 F/L, 8 F/L, 8 F/L, 10 F/L ormore, e.g., in the range of about 1 to about 10 F/L or any sub-rangethereof.

In some embodiments, ultracapacitors of the types described herein mayexhibit any of: a high volumetric energy density (e.g., exceeding 0.25Wh/L, 0.5 Wh/L, 1 Wh/L, 2 Wh/L, 3 Wh/L, 4 Wh/L, 5 Wh/L, 6 Wh/L, 7 Wh/L,8 Wh/L, 9 Wh/L, 10 Wh/L, 11 Wh/L, 12 Wh/L, 15 Wh/L, 18 Wh/L, 20 Wh/L, ormore), a high gravimetric energy density (e.g., exceeding 5 Wh/kg, 6Wh/kg, 7 Wh/kg, 8 Wh/kg, 9 Wh/kg, 10 Wh/kg, 11 Wh/kg, 12 Wh/kg, 15Wh/kg, 18 Wh/kg, or more), a high volumetric power density (e.g.,exceeding 30 kW/L, 40 kW/L, 50 kW/L, 60 kW/L, 70 kW/L, 80 kW/L, 90 kW/L,100 kW/L, 110 kW/L, 120 kW/L, or more), a high gravimetric power density(e.g., exceeding 30 kW/kg, 40 kW/kg, 50 kW/kg, 60 kW/kg, 70 kW/kg, 80kW/kg, 90 kW/kg, 100 kW/kg, 110 kW/kg, 120 kW/kg or more), andcombinations thereof. In some embodiments, ultracapacitors of the typesdescribed herein demonstrate high performance as indicated by theproduct of energy density and power density, e.g., exceeding 300Wh-kW/L{circumflex over ( )}2, 500 Wh-kW/L{circumflex over ( )}2, 700Wh-kW/L{circumflex over ( )}2, or more.

Exemplary Ultracapacitor Performance

Ultracapacitors fabricated according the techniques described hereinmay, for example, operate at temperatures as high as 350 degrees Celsiusor more for 10,000 charge/discharge cycles and/or over 100 hours or moreat a voltage of 0.5 V or more while exhibiting and increase in ESR orless than 100%, e.g. less than about 85% and a decrease in capacitanceof less than about 10%. In some embodiments, such ultracapacitors mayhave a volumetric capacitance of about 5 Farad per liter (F/L), 6 F/L, 7F/L, 8 F/L, 8 F/L, 10 F/L or more, e.g., in the range of about 1 toabout 10 F/L or any sub-range thereof.

In some embodiments, ultracapacitors of the types described herein mayexhibit any of: a high volumetric energy density (e.g., exceeding 5Wh/L, 6 Wh/L, 7 Wh/L, 8 Wh/L, 9 Wh/L, 10 Wh/L. 11 Wh/L, 12 Wh/L, 15Wh/L, 18 Wh/L, 20 Wh/L, or more), a high gravimetric energy density(e.g., exceeding 5 Wh/kg, 6 Wh/kg, 7 Wh/kg, 8 Wh/kg, 9 Wh/kg, 10 Wh/kg,11 Wh/kg, 12 Wh/kg, 15 Wh/kg, 18 Wh/kg, or more), a high volumetricpower density (e.g., exceeding 30 kW/L, 40 kW/L, 50 kW/L, 60 kW/L, 70kW/L, 80 kW/L, 90 kW/L, 100 kW/L, 110 kW/L, 120 kW/L, or more), a highgravimetric power density (e.g., exceeding 30 kW/kg, 40 kW/kg, 50 kW/kg,60 kW/kg, 70 kW/kg, 80 kW/kg, 90 kW/kg, 100 kW/kg, 110 kW/kg, 120 kw/KGor more), and combinations thereof. In some embodiments, ultracapacitorsof the types described herein demonstrate high performance as indicatedby the product of energy density and power density, e.g., exceeding 300Wh-kW/L{circumflex over ( )}2, 500 Wh-kW/L{circumflex over ( )}2, 700Wh-kW/L{circumflex over ( )}2 or more or 300 Wh-kW/kg{circumflex over( )}2, 500 Wh-kW/kg{circumflex over ( )}2, 700 Wh-kW/kg{circumflex over( )}2, or more.

In some embodiments, the ultracapacitors disclosed herein are capable ofmaintaining their performance over a long period of time, e.g., hundredsof thousands, or even millions of charge/discharge cycles. In some suchembodiments, cell lifetime is defined as the number of cycles requiredbefore the cell exhibits a reduction in discharge energy of 5% or moreor an increase in ESR of 25% or more.

As trade-offs may be made among various demands of the ultracapacitor(for example, voltage and temperature) performance ratings for theultracapacitor may be managed (for example, a rate of increase for ESR,capacitance) may be adjusted to accommodate a particular need. Note thatin reference to the foregoing, “performance ratings” is given agenerally conventional definition, which is with regard to values forparameters describing conditions of operation.

Note that measures of capacitance as well as ESR, as presented herein,follow generally known methods. Consider first, techniques for measuringcapacitance.

Capacitance may be measured in a number of ways. One method involvesmonitoring the voltage presented at the capacitor terminals while aknown current is drawn from (during a “discharge”) or supplied to(during a “charge”) of the ultracapacitor. More specifically, we may usethe fact that an ideal capacitor is governed by the equation:

I=C*dV/dt,

where I represents charging current, C represents capacitance and dV/dtrepresents the time-derivative of the ideal capacitor voltage, V. Anideal capacitor is one whose internal resistance is zero and whosecapacitance is voltage-independent, among other things. When thecharging current is I constant, the voltage V is linear with time, sodV/dt may be computed as the slope of that line. However, this method isgenerally an approximation and the voltage difference provided by theeffective series resistance (the ESR drop) of the capacitor should beconsidered in the computation or measurement of a capacitance. Theeffective series resistance (ESR) may generally be a lumped elementapproximation of dissipative or other effects within a capacitor.Capacitor behavior is often derived from a circuit model comprising anideal capacitor in series with a resistor having a resistance valueequal to the ESR. Generally, this yields good approximations to actualcapacitor behavior.

In one method of measuring capacitance, one may largely neglect theeffect of the ESR drop in the case that the internal resistance issubstantially voltage-independent, and the charging or dischargingcurrent is substantially fixed. In that case, the ESR drop may beapproximated as a constant and is naturally subtracted out of thecomputation of the change in voltage during said constant-current chargeor discharge. Then, the change in voltage is substantially a reflectionof the change in stored charge on the capacitor. Thus, that change involtage may be taken as an indicator, through computation, of thecapacitance.

For example, during a constant-current discharge, the constant current,I, is known. Measuring the voltage change during the discharge, Delta V,during a measured time interval DeltaT, and dividing the current value Iby the ratio Delta V/DeltaT, yields an approximation of the capacitance.When the current I is measured in Amperes, DeltaV in volts, and DeltaTin seconds, the capacitance result will be in units of Farads.

Turning to estimation of ESR, the effective series resistance (ESR) ofthe ultracapacitor may also be measured in a number of ways. One methodinvolves monitoring the voltage presented at the capacitor terminalswhile a known current is drawn from (during a “discharge”) or suppliedto (during a “charge”) the ultracapacitor. More specifically, one mayuse the fact that ESR is governed by the equation:

V=I*R,

where I represents the current effectively passing through the ESR, Rrepresents the resistance value of the ESR, and V represents the voltagedifference provided by the ESR (the ESR drop). ESR may generally be alumped element approximation of dissipative or other effects within theultracapacitor. Behavior of the ultracapacitor is often derived from acircuit model comprising an ideal capacitor in series with a resistorhaving a resistance value equal to the ESR. Generally, this yields goodapproximations of actual capacitor behavior.

In one method of measuring ESR, one may begin drawing a dischargecurrent from a capacitor that had been at rest (one that had not beencharging or discharging with a substantial current). During a timeinterval in which the change in voltage presented by the capacitor dueto the change in stored charge on the capacitor is small compared to themeasured change in voltage, that measured change in voltage issubstantially a reflection of the ESR of the capacitor. Under theseconditions, the immediate voltage change presented by the capacitor maybe taken as an indicator, through computation, of the ESR.

For example, upon initiating a discharge current draw from a capacitor,one may be presented with an immediate voltage change DeltaV over ameasurement interval DeltaT. So long as the capacitance of thecapacitor, C, discharged by the known current, I, during the measurementinterval, DeltaT, would yield a voltage change that is small compared tothe measured voltage change, DeltaV, one may divide DeltaV during thetime interval DeltaT by the discharge current, I, to yield anapproximation to the ESR. When I is measured in Amperes and DeltaV inVolts, the ESR result will have units of Ohms.

Both ESR and capacitance may depend on ambient temperature. Therefore, arelevant measurement may require the user to subject the ultracapacitorto a specific ambient temperature of interest during the measurement.

Performance requirements for leakage current are generally defined bythe environmental conditions prevalent in a particular application. Forexample, with regard to a capacitor having a volume of 20 mL, apractical limit on leakage current may fall below 100 mA. As referred toherein, a “volumetric leakage current” of the ultracapacitor generallyrefers to leakage current divided by a volume of the ultracapacitor, andmay be expressed, for example in units of mA/cc. Similarly, a“volumetric capacitance” of an ultracapacitor generally refers tocapacitance of the ultracapacitor divided by the volume of theultracapacitor, and may be expressed, for example in units of F/cc.Additionally, “volumetric ESR” of the ultracapacitor generally refers toESR of the ultracapacitor multiplied by the volume of theultracapacitor, and may be expressed, for example in units of Ohms*cc.

Note that one approach to reduce the volumetric leakage current at aspecific temperature is to reduce the operating voltage at thattemperature. Another approach to reduce the volumetric leakage currentat a specific temperature is to increase the void volume of theultracapacitor. Yet another approach to reduce the leakage current is toreduce loading of the energy storage media on the electrode of theultracapacitor.

A variety of environments may exist where an ultracapacitor of the typedescribed herein is of particular usefulness. For example, in automotiveapplications, ambient temperatures of 105 degrees Celsius may berealized (where, in some embodiments, a practical lifetime of someexemplary ultracapacitors will range from about 1 year to 20 years). Insome downhole applications, such as for geothermal well drilling,ambient temperatures of 250 degrees Celsius or more may be reached(where, in some embodiments, a practical lifetime of some exemplaryultracapacitors will range from about 100 hours to 10,000 hours).

A “lifetime” for an ultracapacitor is also generally defined by aparticular application and is typically indicated by a certainpercentage increase in leakage current or degradation of anotherparameter (as appropriate or determinative for the given application).For instance, in one embodiment, the lifetime of an ultracapacitor in anautomotive application may be defined as the time at which the leakagecurrent increases to 200% of its initial (beginning of life or “BOL”)value. In another embodiment, the lifetime for an ultracapacitor in adownhole application may be defined based on the increase of its ESRfrom its initial BOL value, e.g., the lifetime may be defined as thetime at which the ESR increases to 50%, 75%, 100%, 150%, or 200% of itsBOL value.

As used herein, “peak power density” is one fourth times the square ofpeak device voltage divided by the effective series resistance of thedevice. “Energy density” is one half times the square of the peak devicevoltage times the device capacitance.

Nominal values of normalized parameters may be obtained by multiplyingor dividing (as appropriate) the normalized parameters (e.g. volumetricleakage current) by a normalizing characteristic (e.g. volume). Forinstance, the nominal leakage current of an ultracapacitor having avolumetric leakage current of 10 mA/cc and a volume of 50 cc is theproduct of the volumetric leakage current and the volume, 500 mA.Meanwhile the nominal ESR of an ultracapacitor having a volumetric ESRof 20 mOhm*cc and a volume of 50 cc is the quotient of the volumetricESR and the volume, 0.4 mOhm.

CONCLUSION

While various inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the inventive embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific inventive embodiments described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that, within the scope of the appended claimsand equivalents thereto, inventive embodiments may be practicedotherwise than as specifically described and claimed. Inventiveembodiments of the present disclosure are directed to each individualfeature, system, article, material, kit, and/or method described herein.In addition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the inventive scope of the present disclosure.

Various embodiments described herein are to be understood in both openand closed terms. In particular, additional features that are notexpressly recited for an embodiment may fall within the scope of acorresponding claim, or can be expressly disclaimed (e.g., excluded bynegative claim language), depending on the specific language recited ina given claim.

Unless otherwise stated, any first range explicitly specified also mayinclude or refer to one or more smaller inclusive second ranges, eachsecond range having a variety of possible endpoints that fall within thefirst range. For example, if a first range of 3 V>X>10 V is specified,this also specifies, at least by inference, 4 V<x<9 V, 4.2 V<x<8.7 V,and the like.

Also, various inventive concepts may be embodied as one or more methods,of which an example has been provided. The acts performed as part of themethod may be ordered in any suitable way. Accordingly, embodiments maybe constructed in which acts are performed in an order different thanillustrated, which may include performing some acts simultaneously, eventhough shown as sequential acts in illustrative embodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of or “exactly one of,” or, when used inthe claims, “consisting of,” will refer to the inclusion of exactly oneelement of a number or list of elements. In general, the term “or” asused herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of and “consistingessentially of shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

What is claimed is:
 1. A solid state electrolyte for use in anultracapacitor comprising: a polymer matrix doped with an ionic liquidand two solvents—a first solvent and a second solvent; where the secondsolvent has a melting point lower than the first solvent; where thefirst solvent has a dielectric constant at 25° C. greater than about 2;and wherein an ultracapacitor that utilizes the electrolyte isconfigured to output electrical energy at temperatures throughout anoperating temperature range.
 1. The electrolyte of claim 1, wherein theoperating temperature range comprises 0 degrees Celsius to 275 degreesCelsius.
 3. The electrolyte of claim 1, wherein the ultracapacitor thatutilizes the electrolyte is configured to output electrical energy atoperating voltages throughout an operating voltage range, the operatingvoltage range being between about 0 V and about 0.5 V.
 4. Theelectrolyte of claim 1, where the solid state electrolyte is castdirectly onto an electrode in the ultracapacitor.
 5. The electrolyte ofclaim 1, where the first solvent comprises acetonitrile, trimethylamine,propylene carbonate or gamma-butyrolactone.
 6. The electrolyte of claim1, where the second solvent comprises methyl formate, ethyl acetate,methyl acetate, propionitrile, butyronitrile or 1,3-dioxolane.
 7. Theelectrolyte of claim 1, where the second solvent may has a melting pointthat is lower than the boiling point of the first solvent by at least10° C.
 8. The electrolyte of claim 1, wherein the ionic liquid comprisesa cation comprising at least one of: tetrabutylammonium,1-(3-cyanopropyl)-3-methylimidazolium, 1,2-dimethyl-3-propylimidazolium,1,3-bis(3-cyanopropyl)imidazolium, 1,3-diethoxyimidazolium,1-butyl-1-methylpiperidinium, 1-butyl-2,3-dimethylimidazolium,1-butyl-3-methylimidazolium, 1-butyl-4-methylpyridinium,1-butylpyridinium, 1-decyl-3-methylimidazolium,1-ethyl-3-methylimidazolium, 1-pentyl-3-methylimidazolium,1-hexyl-3-methylimidazolium, 3-methyl-1-propylpyridinium, or acombination thereof.
 9. The electrolyte of claim 1, wherein the ionicliquid comprises a cation comprising at least one of: ammonium,imidazolium, pyrazinium, piperidinium, pyridinium, pyrimidinium, andpyrrolidinium and combinations thereof.
 10. The electrolyte of claim 1,wherein the ionic liquid comprises a anion comprising at least one of:bis(trifluoromethanesulfonate)imide,tris(trifluoromethanesulfonate)methide, dicyanamide, tetrafluoroborate,tetra(cyano)borate, hexafluorophosphate,tris(pentafluoroethyl)trifluorophosphate, trifluoromethanesulfonate,bis(pentafluoroethanesulfonate)imide, thiocyanate,trifluoro(trifluoromethyl)borate, and combinations thereof.
 11. Theelectrolyte of claim 1, further comprising at least one additive. 12.The electrolyte of claim 11, wherein the additive comprises a porousinorganic oxide.
 13. The electrolyte of claim 12, wherein the porousinorganic oxide comprises at least one of silica, silicates, alumina,titania, magnesia, aluminosilicates, zeolites, titanates, orcombinations thereof.
 14. The electrolyte of claim 11, wherein theadditive comprises silica or silicates.
 15. The electrolyte of claim 11,wherein the additive comprises a mesoporous inorganic oxide.
 16. Theelectrolyte of claim 11, wherein the additive comprises a gelling agentthat comprises a polycrystalline inorganic oxide.
 17. The electrolyte ofclaim 11, wherein the additive comprises a gelling agent that comprisesa microcrystalline inorganic oxide.
 18. The electrolyte of claim 11,wherein the additive comprises a material with a specific surface area(SSA) above about 400 m²/g.
 19. The electrolyte of claim 1, wherein theultracapacitor that utilizes the electrolyte is configured to outputelectrical energy at operating voltages throughout an operating voltagerange, the operating voltage range being between about 0 V and about 0.5V.
 20. The electrolyte of claim 1, wherein at least one solvent of thetwo solvents is a gas at 0° C. and 760 mm Hg.